The Double Crystal Analyzer Linkage (DXAL) is one of 20 being installed in the Multi-Axis Crystal

Spectrometer (MACS). Visible are two curved panels holding pyrolytic graphite crystals and collima

blades between them. The design features a single mechanical linkage that allows rotation of each cr

panel by 2θ and each blade by θ while maintaining parallel entering and exiting beam paths.
ACCOMPLISHME

AND OPPORTUNIT

NIST Special Publicatio

Patrick D. Gallaghe

Ronald L. Cappell

Septe

National Institute of Standards and T

William A. Jeffre

Technology Adm

Miche

Acting Under S

Commerce for T

U.S. Department of 

Carlos M. Gutierrez
ii

DISCLAIMER

Certain commercial entities, equipment, or materials may be identified

in this document in order to describe an experimental procedure or

concept adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards

and Technology, nor is it intended to imply that the entities, materials,

or equipment are necessarily the best available for the purpose.

National Institute of Standards 

and Technology Special Publication 1045

Natl. Inst. Stand. Technol. Spec. Publ. 1045, 72 pages 

(September 2005)

CODEN: NSPUE2

U.S. GOVERNMENT PRINTING OFFICE - WASHINGTON: 2005

For sale by the Superintendent of Documents, 

U.S. Government Printing Office

Internet: bookstore.gpo.gov ■ Phone: 202.512.1800 

Fax: 202.512.2250 ■ Mail: Stop SSOP, Washington, DC 20402-0001
CHEMICAL PHYSICS

Hydrogen Adsorption Sites and Nanocage Formation 

in Metal-organic Frameworks . . . . . . . . . . . . . . . . . . . . . . . . . 6

Ti-decorated Carbon Nanostructures for Potential 

High-capacity Hydrogen Storage . . . . . . . . . . . . . . . . . . . . . . . 8

Pressure Dependence of Transitions in Supercooled, 

Confined Liquid Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Diffusion of Water on Zirconia Nanoparticles . . . . . . . . . . . . 12

Cement: The Hydration of Tricalcium and Dicalcium 

Silicate Mixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

SOFT MATTER/POLYMERS

Phase Behavior and Local Dynamics of Concentrated 

Triblock Copolymer Micelles . . . . . . . . . . . . . . . . . . . . . . . . . 16

Rheo-SANS: Gap-Resolved SANS of Shear-induced 

Alignment of Wormlike Micelles . . . . . . . . . . . . . . . . . . . . . . 18

Segregation in Polymer Blend Film Interfaces: Effects 

of Chain Ends and Node Points . . . . . . . . . . . . . . . . . . . . . . . 20

BIOLOGY

Protein Incorporation in Solid-supported Model 

Lipid Membranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Polyunsaturated Lipids: Neutrons Complete the Story... . . . . 24

Methyl Dynamics as a Probe of Protein 

Structure and Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Neutron Scattering Study of Spin Excitations i

Singlet Ground State of SrCu2(BO3)2 . . . . . . . 

Persistence and Memory of Polar Nanoregions 

a Ferroelectric Relaxor in an Electric Field . . . 

Spin Chirality on a Two-dimensional Frustrate

Inter-granular Giant Magnetoresistance in a Sp

Phase Separated Perovskite . . . . . . . . . . . . . . 

Magnetism and Ferroelectricity in HoMnO3 an

ENGINEERING PHYSICS

3D Imaging of Microstrains During Single Grain 

Neutron Residual Stress Measurements for Im

Safety of Gas Pipelines . . . . . . . . . . . . . . . . . . 

ADVANCES IN MEASUREMENT

Crystal Orientation from Laue Diffraction Patt

Very Compact High Performance Microchann

Neutron Collimators . . . . . . . . . . . . . . . . . . . . 

INAA for Small Samples and New SRMs for S

Sampling Instruments. . . . . . . . . . . . . . . . . . . 

SERVING THE SCIENCE AND TECHNOLOGY CO

OPERATIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

FACILITY DEVELOPMENTS . . . . . . . . . . . . . . . . . . 

AWARDS 2005 . . . . . . . . . . . . . . . . . . . . . . . . . . . 

PUBLICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

INSTRUMENTS AND CONTACTS. . . . . . . . . . . . 
gp

scheduled three-month shutdown

to replace the cadmium control

assemblies (“shim arms”) for the

reactor and to replace the heavy

water in order to reduce the concentration of tritium in the reactor 

primary cooling circuit. Our staff took advantage of the outage to perform a large number of maintenance projects and upgrades to the reactor,

the beam systems, and the instruments. In spite of the long list of tasks,

all work was completed on time and the reactor and cold source performed flawlessly for the remainder of the year, during which it operated

197 full power days. This year has also seen enormous progress made on

the installation of two major new instruments: a thermal triple-axis 

spectrometer located at BT-7 and a cold neutron multi-analyzer crystal

spectrometer at NG-0. Both instruments are in the advanced stages of

construction and will provide major advances in capability when completed. 

The budget setback that so adversely affected the NCNR in 2004 was

reversed in dramatic fashion with the passage of the 2005 budget. Not

only was lost funding restored, but significant new funds were added to

expand the user program and instrument development programs at the

NCNR. The success of this budget initiative, originally proposed in 2002,

was due to the strong and vocal support of the NCNR by its 

many users who lobbied and wrote to the Administration and to

Congress. Their show of support is deeply gratifying and appreciated by

all of us here at the NCNR. For our part, we are already working hard to

develop new and improved instruments and to increase access to these

instruments through a stronger user program. 

NCNR after 39 years at the National Bureau of S

those years as head of the science effort at the N

formally joining NBS, Jack worked on projects w

NBS Reactor. His career thus spans the entire hi

its construction to its growth into today’s leadin

strong leadership and steady presence have guid

Jack’s wisdom and friendship have also benefite

here and of the thousands of researchers who h

knowledge and advice have strongly influenced 

tron science in the United States. Dan Neumann 

of the Neutron Condensed Matter Science group

an active research program at the NCNR.

In another significant change, Sy Weiss announc

federal service this year. Sy came to NIST in 199

Chief of Reactor Operations and Engineering sin

bility for the operation of the reactor and for the 

reactor operating license. However Sy’s influenc

long before he came to NIST. As Director of the 

Decommissioning Project at the Nuclear Regula

responsible for establishing and implementing a 

for research and test reactors, which includes th

clear and important distinctions between non-p

Wade Richards, who joined NIST in 2003 will a

duties for Reactor Operations and Engineering a

With this brief synopsis of the major “news” of 

to enjoy the following summaries of research hi

many results of the past year, they reflect the hi

breadth of the research performed at the NCNR

what makes all of the other efforts worthwhile!

iv
Neutrons are powerful probes of the structure and dynamics of materials

ranging from molecules inserted into membranes that mimic cell walls to

protons migrating through fuel cells. The unique properties of neutrons

(discussed below) can be exploited using a variety of measurement techniques to provide information not available by other means. They are

particularly well suited to investigate all forms of magnetic materials such

as those used in computer memory storage and retrieval. Atomic motion,

especially that of hydrogen, can be measured and monitored, like that of

water during the setting of cement. Residual stresses such as those inside

stamped steel automobile parts can be mapped. Neutron-based research

covers a broad spectrum of disciplines, including engineering, biology,

materials science, polymers, chemistry, and physics.

The NCNR’s neutron source provides the intense beams of neutrons

required for these types of measurements. In addition to the thermal neutron beams from the heavy water or graphite moderators, the NCNR has

a large area liquid hydrogen moderator, or cold source, that provides

intense neutron beams for the only dedicated cold neutron facility

presently operating in the U.S.

There are currently 29 experiment stations: four provide high neutron

flux positions for irradiation and 25 are beam facilities most of which are

used for neutron scattering research. The following pages show a

schematic layout of the beam facilities. More complete descriptions of the

instruments can be found at www.ncnr.nist.gov.

The NCNR supports important NIST research needs, but is also operated

as a major national user facility with merit-based access made available to

the entire U.S. technological community. Each year, about 2000 research

participants from all areas of the country, from industry, academia, and

government use the facility for measurements. Beam time for research to

be published in the open literature is without cost to the user, but full

science staff can also be arranged on other instrumen

WHY NEUTRONS?

Neutrons reveal properties not available to other prob

behave like microscopic magnets, they can diffract lik

set particles into motion losing or gaining energy and 

process, and they can be absorbed.

WAVELENGTHS—range from 0.1 Å to 100 Å (1 Å 

them to form observable ripple patterns from structu

to as large as proteins. At the NCNR, incident neutro

from ~ 0.5 Å to ~ 20 Å.

ENERGIES—of millielectronvolts, of the same order a

atoms in solids or liquids, waves in magnetic materials

molecules. Exchanges of energy between neutrons and 

nanoelectronvolts and as large as tenths of electronvolt

SELECTIVITY—in scattering power varies from nucl

somewhat randomly. Specific isotopes can stand out 

Specific light atoms, difficult to observe with x-rays, 

neutrons. Hydrogen, especially, can be distinguished 

equivalent deuterium.

MAGNETISM—makes the neutron sensitive to the m

both nuclei and electrons, allowing the behavior of o

magnets to be detailed precisely. 

NEUTRALITY—of the uncharged neutrons allows th

deeply without destroying samples, and pass through 

sample’s environment allowing measurements under 

Properties ranging from the residual stresses in steel g

unfolding motions of proteins are amenable to measu

and water moving within fuel cells can be imaged.

CAPTURE—characteristic radiation emanating from 

turing incident neutrons can be used to identify and 

amounts of material in pollutants or ancient pottery s
1

2

3

5 4

6

7

8

9

10

25

11

12

13

2

24

2
14

15

16

17

18

19

20

21

22

3

p

filter analyzer for chemical spectroscopy.

10. BT-5 Perfect Crystal Diffractometer SANS

small angle neutron scattering instrument

for microstructure up to 104 nm, sponsored by the National Science Foundation

and NIST, part of the Center for High

Resolution Neutron Scattering (CHRNS). 

g

dynamics from 100 ns to 10 ps, in partnership with ExxonMobil—part of CHRNS.

15. Prompt Gamma Activation Analysis

cold neutron fluxes allow detection limit

for H of 1 μg to 10 μg. Focused beams are

available for profiling. 

16. NG-7 30 m SANS for microstructure

measurements, in partnership with NIST,

ExxonMobil, and the Cold Neutrons for

Biology and Technology program. 

17. Neutron Physics Station offering three cold

neutron beams having wavelengths of 0.5

nm, 0.9 nm, and “white” that are available for

fundamental neutron physics experiments. 

21. Backscattering Spect

intensity inelastic scatt

with energy resolution 

of motion in molecular 

systems—part of CHR

22. A Cold Neutron Depth 

ment (not shown) for 

of subsurface impuritie

site will be moved to a

Shown is the NG-1 10 

under construction.

23. Vertical Sample Reflec

with polarization analy

measuring reflectivities 

determine subsurface s

24. Advanced Neutron Dif

Reflectometer (AND/R

reflectometer with pola

off-specular reflection c

uring reflectivities down 

Cold Neutrons for Biolo

program committed to 

membrane systems.

25. Thermal Neutron Capt

Gamma-ray Activation 

at VT-5 with a neutron 

of 3 x 108 /cm2/s used 

elemental analysis of b

Generally used for the 

hydrogenous materials 

foods, oils, and biologi
4

[2] [3]

[4] [5]

[6]

[3] NCNR’s John Copley (left) guid

workshop participants.

[4] SURF student Stephanie Moyerman prepares to

mount a displex refrigerator.

[5] Confident Richard Azuah, Larry Kneller, and Rob

Dimeo of the DAVE team.

[6] 2005 SURF students: Andrew Gardner, SUNY at

Binghamton, Atiq Chowdhury, George Washington U.,

Stephanie Moyerman, Harvey Mudd Coll., Teresa

Jacques, Smith Coll., Veronica Rodriguez, U. of Puerto

Rico, and Daniel Miller, Bucknell U.
[9]

[10]

[13 ]

[12 ]

[10] Amnon Aharony and Ora Entin

Wohlman (Tel Aviv) ponder a p

Brooks Harris (Penn).

[11] Olivier Isnard (CNRS) and Tobias

Futterer (Rhodia) model neutron scattering on the lawn.

[12] Collaborators Thomas Hauet (Nancy),

Philippe Mangin (LLB), and Julie

Borchers (NCNR) caught off guard

working.

[13] Bruce Gaulin, Jacob Ruff, Kirrily Rule,

and Pat Clancy, all of McMaster U.,

happily pursue magnetic frustration at

the DCS.
The success of future hydrogen and fuel cell technologies is

critically dependent upon the discovery of new materials that

can store large amounts of hydrogen under ambient conditions.

Metal-organic framework (MOF) compounds, which consist of

metal-oxide clusters connected by organic linkers, are a relatively new class of nano-porous material that show promise

for hydrogen storage applications because of their tunable

pore size and functionality. Yet despite numerous experimental studies of hydrogen adsorption in MOF materials, the

nature of the MOF-hydrogen interaction and the manner in

which hydrogen molecules are adsorbed onto the structure

are still unknown. Answers to these questions hold the 

key to optimizing these materials for practical hydrogen 

storage applications. 

Here we use the difference-Fourier analysis of neutron powder diffraction

data together with first-principles total-energy calculations[1,2], to 

directly determine the H2 adsorption sites in MOF5 (the most widely

studied MOF material, which consists of ZnO4 clusters linked by 

1,4-benzenedicarboxylate (BDC)). Surprisingly, we find that the MOF5

host lattice has enough space available to hold many hydrogen molecules,

up to a mass fraction of ≈ 11 % at low temperatures. The ZnO4-cluster is

responsible for most of the adsorption while the organic linker plays only a

secondary role. Equally important, we discover that at high concentration

loadings hydrogen molecules form 3-dimensional (3D) networks of H2

nano-clusters with intermolecular distances of 3.0 Å, which is significantly

shorter than the intermolecular distances of 3.6 Å in pure solid hydrogen.

These findings [1,2] suggest that MOF materials can also be used as templates to create artificial, interlinked hydrogen nanocages. Such materials

could exhibit very unexpected properties due to confinement effects and

small intermolecular separation, such as metallic behavior. 

FIGURE 1: The neutron powder diffraction pattern 

MOF5-4D2 at 3.5 K (dots) plus the Rietveld refine

with space group Fm3m and a = 25.91 Å, and diffe

The inset shows the real-space difference-Fourier s

density superimposed on the MOF5 structure, indi

cup-sites for the first hydrogen adsorption (red-yel

Due to the large incoherent cross section of H2, 

data were collected on a MOF5 sample with the 

with D atoms, which was synthesized as describ

The diffraction data from this MOF5 host lattice 

excellent agreement with the refinement and all

positions of the BDC linker to be determined fo

characterized the MOF5 host lattice, we studied 

terium in MOF5 as a function of D2 concentrati

(i.e., per 4Zn). The sample was loaded with nD2 

trations: n = 4, 8, 14, 26, 34, and 44 D2. We no

corresponds to a mass fraction hydrogen uptake 

of the structural refinements of the deuterium lo

any evidence of solid D2, indicating that the deu

onto the MOF5. 

6

10 20 30 40 50 

2 [degrees]

Neutron count/hour (x1000)

0

8

6

4

2

MOF5-4D2
Figure 1 shows the diffraction pattern from MOF5 that was loaded with

4 D2/4Zn. In order to locate the hydrogen adsorption sites, we first performed a Rietveld structural refinement using the model for the MOF5

host structure, ignoring the adsorbed D2 molecules. The differenceFourier scattering length density based upon this model, shown in the

inset to Fig.1, was then used to locate the adsorbed D2 molecules. The

Fourier plot clearly shows where the hydrogen molecules are adsorbed

(red-yellow-green region). The first adsorption sites (blue) are the positions at the center of the three ZnO3 triangular faces, which resemble a

cup shape and were termed the “cup-sites”. There are four such sites,

forming a tetrahedral cluster (blue region in Fig. 2(a)). Having determined the location of the first-adsorption sites, we further refined the

structural model, explicitly including the D2 molecules at the first

adsorption site. The positions, isotropic thermal factors, and fractional

occupancies of the adsorbed D2 molecules were refined. The deuterium

molecules were treated as point scatterers with double occupancy. The

final refinement for a deuterium loading of 4D2/4Zn is shown in Fig.1.

For the 4D2/4Zn loading, we also observed a small amount of D2

(i.e., 10 %) adsorbed at a secondary adsorption site (green isosurface in

Fig. 2(a)). For 8D2/4Zn loading, these two adsorption sites are almost

fully occupied. Unlike the cup-sites, the second adsorption sites are on

top of single ZnO3 triangles and were hence denoted as “ZnO3-sites”. 

We observed that with further hydrogen loading (i.e., 14 and 26

D2/4Zn), there are two additional adsorption sites that start to populate

in almost equal proportion. These sites are shown in Fig. 2(b) as lightblue and brown spheres. The adsorption sites just above the two oxygen

ions are called the “ZnO2-sites”. The fourth adsorption site is basically

the top of the hexagonal linkers, which we termed the “Hex-site”. The

refined fractional-occupancy positions of these four sites are summarized

in Fig. 2. At 26 D2/4Zn loading, structural refinement indicates that these

four adsorption sites are almost totally occupied yielding a H2-uptake

mass fraction of 6.8 %.

nanocage structures. These results suggest that the M

be used as templates to build new artificial hydrogen 

which could have interesting properties due to the qu

molecules, confinement effects, and small intermolec

FIGURE 3: Two different hydrogen nanocages (blue and 

obtained from Rietveld refinements at (a) 34 and (b) 46 

respectively. For clarity, only some of the ZnO3 (red-pin

(grey-black) are shown.

In conclusion, using Rietveld structural refinement o

diffraction data in conjunction with difference-Fourie

principles calculations, we have determined the hydr

sites and binding energies in MOF5 as a function of h

[1,2]. The results not only hold the key to optimizing 

hydrogen storage applications but also suggest that M

templates to create artificial interlinked hydrogen nan

properties.

REFERENCES

[1] For more information see http://www.ncnr.nist.go

[2] T. Yildirim and M. R. Hartman, Phys. Rev. Lett. (c

a. b.
Developing safe, cost-effective, and practical means of storing

hydrogen is crucial for the advancement of fuel-cell technologies. The current state-of-the-art is at an impasse in providing

any materials that meet a > 6 % mass fraction hydrogen storage capacity required for practical applications. Much effort

has been focused on the engineering of carbon-based materials

such as nanotubes and transition metal hydrides without success. It is found that while the hydrogen-carbon interaction is

too weak [1], the metal-hydrogen interaction is too strong for

room temperature reversible storage. Using state-of-the-art

first-principles calculations, we show here a novel way [1-4] 

to overcome this difficulty by forming artificial metal-carbide

like structures on nanotubes [2] and C60 molecules [3]. 

Recent experiments and calculations suggest that it may be possible to

coat carbon nanotubes uniformly with certain transition metals. A single

Ti atom on an (8,0) single-wall nanotube (SWNT) has a magnetic ground

state with S = 1 and a binding energy of 2.2 eV; this will serve as our reference system, denoted t80Ti. Figure 1a shows the energy variation as a

single H2 molecule approaches t80Ti. The energy first decreases slowly

as the hydrogen gets closer to the nanotube and Ti. However, as the

charge overlap gets large, the H2 molecule is attracted towards the Ti

atom with a sudden decrease in the energy. At this point, the H2 molecule is still intact. The second sudden decrease in energy is achieved by

dissociating the H2 molecule into two H atoms. The interaction between

H2 and t80Ti is always attractive and therefore H2 is absorbed onto a 

Ti atom without any energy barrier. The energy gain through this 

dissociative adsorption is about 0.83 eV with respect to spin-polarized

calculations for the isolated H2 and t80Ti systems. 

Remarkably, it is also energetically favorable for 

plex with additional hydrogen molecules. Figur

variation as two hydrogen molecules approach t

each side of the TiH2 group. As in the case of si

gy always decreases, first slowly and later very r

both hydrogen molecules are strongly attached 

8
We denote the final product as t80TiH2- 2H2. The total energy change

upon adsorption is about 0.89 eV (i.e., 0.45 eV/H2). Unlike the first

adsorption, the two hydrogen molecules are intact but with a rather 

elongated bond length of 0.81 Å. 

Figure 1c shows the energy evolution when a fourth hydrogen molecule

approaches the t80TiH2-2H2 system from the top. The energy again

decreases continuously, indicating a zero-energy barrier. The final product, denoted as t80TiH2-3H2, is shown in the inset. The energy gained

by the fourth adsorption, 0.34 eV/H2, is slightly smaller than for the

other cases but is still substantial. The H-H distance of the top H2 is 

0.86 Å. Several attempts to add a fifth hydrogen molecule at a variety 

of positions failed, suggesting a limit of 4 H2/Ti.

The final optimized structures shown in Fig.1 need not be the global

minimum. Among many different isomers tried for the four-H2 system,

we found a very symmetric configuration (denoted as t80Ti- 4H2) that is

0.1 eV lower in energy than t80TiH2- 3H2 (Fig. 2a). Here all four hydrogen molecules stay intact and benefit equally from bonding with the Ti

atom. The average H-H bond distance is about 0.84 Å and each molecule

has a charge of about 0.32 e. The average binding energy per H2 molecule is 0.54 eV, which suggests that the bonding is an unusual combination of chemisorption and physisorption. Also note that each of the four

H2 molecules is located just above one of the four carbons of the hexagon over which the Ti atom is bonded. This suggests that carbon atoms

also play an important role in the binding. These results can be explained

by a simple Dewar-Chatt-Duncanson model where the interaction is

caused by donation of charge from the highest occupied orbital of the 

ligand to the metal empty states and a subsequent back donation from

filled d-orbitals to the lowest unoccupied orbital of the ligand. The analysis of the molecular orbitals shown in Fig. 2b supports this mechanism.

indicating that the system has the capacity to accomm

hydrogen atoms. In fact, these configurations, which 

formulas, C4TiH8 and C60Ti14H56, store hydrogen m

approximately 8 % and 7.5 %, respectively. 

FIGURE 3: High-density hydrogen (red) coverage on (a) 

nanotube and (b) C60 .

In conclusion, using accurate first-principles total-en

have shown that light transition metals such as a Ti a

small diameter nanotube/C60 can bind up to four hy

remarkable and totally unanticipated finding. At high 

is possible to store hydrogen reversibly up to a mass 

These results advance our fundamental understandin

molecular chemisorptions of hydrogen in nanostructu

possible method of engineering new nanostructures f

storage and catalyst materials. 

REFERENCES

[1] S.Dag, Y. Ozturk, S. Ciraci, and T. Yildirim, Phys. 

(cond-mat/0504694).

[2] T. Yildirim and S. Ciraci, Phys. Rev. Lett. 94, 175

[3] T. Yildirim, J., and S. Ciraci, Phys. Rev. B (cond-m

[4] For more information see http://www.ncnr.nist.go

a. b.

, g

the involvement of Hantibonding, Ti d-orbitals,

and C π-orbitals in the

bonding mechanism.
Water is essential for all living systems and its properties

impact our daily lives and environment directly. Therefore its

counterintuitive behavior in the supercooled state stimulates

interest in the scientific community. For example, some thermodynamic response functions and transport coefficients show a

tendency to diverge at a singular temperature of 228 K.

However, to date this supercooling behavior has been inaccessible because water inevitably freezes into ice before reaching

this temperature. By confining water in nano-pores of mesoporous silica, we have succeeded in suppressing freezing and

entering the supercooled region in this temperature range.

Using the dynamic neutron scattering method we discovered 

a series of fragile-to-strong transitions in deeply supercooled

water under pressure. We present new experimental findings

that shed light on the nature of the liquid-liquid transition line

and its end point, the anticipated second critical point much 

discussed in recent literature. 

One of the most intriguing questions related to the unusual properties 

of supercooled water is whether two critical points exist in a singlecomponent liquid [1]. The anomalies of the thermodynamic quantities

become plausible if one postulates the existence of a second low-temperature critical point at about 228 K and at somewhat elevated pressure.

Search for the existence of the predicted first-order liquid-liquid transition line [2] and its end point, the second low-temperature critical point

[1] in water, has been hampered by intervention of the homogenous

nucleation process which takes place at 235 K at ambient pressure.

However, by confining water in nano-pores of mesoporous silica MCM41-S with cylindrical pores of 14 Å diameter, we have been able to study

the dynamical behavior of water in a temperature range down to 160 K

without crystallization. Using the high-resolution quasi-elastic neutron

scattering (QENS) method, with the Backscatter

spectrometers at the NCNR [3,4], we have deter

and pressure dependences of the average transla

< τT>, for confined supercooled water using the 

(RCM) [5] for the spectral analysis. < τT> essent

the structural relaxation time of the hydrogen-b

typical water molecule. 

The behavior of the shear viscosity η or equival

relaxation time τ of a supercooled liquid approa

temperature is called ‘fragile’ when it varies acco

Vogel-Fulcher-Tammann (VFT) law; and the beh

when η or τ obeys the Arrhenius law. For water

temperature and at moderately supercooled tem

coworkers [6] proposed that a ‘fragile-to-strong’ 

around 228 K, based on a thermodynamic argu

In Fig. 1, we report the temperature variation o

molecules as a function of pressure. Fig. 1 A, B, 

a transition from a VFT law to an Arrhenius law

Arrhenius to Arrhenius behavior, previously obs

[5], is the signature of a fragile-to-strong dynam

Ito et al. [6]. However, in Fig. 1 E and F, the cus

rounded off and it is no longer possible to defin

transition temperature. 

We show in Fig. 2 the observed pressure depen

strong transition temperature, TL. Also depicted 

and TMD lines. One should note that the TL lin

parallel to the TMD line, indicating a lower densit

phase. This TL line also approximately tracks the 

the upper end by intersecting the TH line at 1600 

Since what we observe experimentally is a dyna

ral to ask whether TL is also a liquid-liquid tran

10
the natures of the high-temperature and low-temperature liquids?

According to our separate inelastic neutron scattering experiments, which

measure the librational density of states of water contained in 18 Å pore

size MCM-41-S, water remains in a disordered liquid state both above

and below the fragile-to-strong transition at ambient pressure.

Furthermore, our analysis indicates that the activation energy barrier for

initiating the local structural relaxation is EA = 20.5 kJ/mol for the lowtemperature phase. On the other hand, our previous inelastic scattering

experiments of the stretch-vibrational band of water [7] indicated that the

effective activation energy for breaking a hydrogen bond at 258 K (in the

high-temperature phase) is 13.4 kJ/mol. Combining these two observations, it is reasonable to conclude that the high-temperature liquid 

corresponds to the high-density liquid (HDL) where the locally tetrahedrallycoordinated hydrogen bond network is not fully developed, while the 

low-temperature liquid corresponds to the low-density liquid (LDL) where

the more open, locally ice-like hydrogen bond network is fully developed. 

Finally, it is important to address the location of the suggested second critical point [2]. We did not observe a clear evidence of critical slowing down

near the low-pressure end of the TL line. However, we did find that TL

ceases to change below 200 bar. An alternative scenario may be that the 

J.R.D. Copley, and C. Brown at NIST NCNR are grea

REFERENCES: 

[1] P. G. Debenedetti, H. E. Stanley, Physics Today 56

[2] P. H. Poole, F. Sciortino, U. Essmann, H. E. Stanle

(1992). 

[3] A. Meyer et al, Rev. Sci. Instrum. 74, 2759 (2003

[4] J. R. D. Copley, J. C. Cook, Chem. Phys. 292, 47

[5] A. Faraone et al, J. Chem. Phys. 121, 10843 (200

[6] K. Ito, C. T. Moynihan, C. A. Angell, Nature 398

[7] M. A. Ricci, S.-H. Chen, Phys. Rev. A 34, 1714 (1

[8] S. Sastry, C. A. Angell, Nature Materials 2, 739 (

0.0045 0.0050 0.0055 0.0060 100

101

102

103

104

0.0045 0.0050 0.0055 0.0060 0.0065 101

102

103

104

1/ T (K-1 1/ T (K ) -1)

<τT> (ps)

F

 Experiment Data

 Guide for the eye

P re s s ure =2400 ba r

E

 Experiment Data

 Guide for the eye

P re s s ure =2000 ba r

FIGURE 1: Temperature dependence of the average translational relaxation

time plotted as log(<τT>) vs T0/T, where T0 is the ideal glass transition 

temperature in the VFT law: (τ = τ0 exp[DT0/(T – T0)]). Data at ambient

pressure, 200 bar, 400 bar, 800 bar, 2000 bar, and 2400 bar are shown in

panels A, B, C, D, E, and F, respectively. In panels A, B, C, and D, there is 

a clear and abrupt transition from a VFT law at high temperature to an

Arrhenius law (τ = τ0 exp[EA/kBT]) at low temperature, with the fitted 

transition temperature TL indicated in the figure. In panels E and F, the 

temperature dependence follows neither the VFT law nor the Arrhenius law, 

and there is no clearly identifiable transition point.

0.0

0.5

1.0

1.5

2.0

2.5

-100 -80 -60 -40 

180 200 220 240 

TL

TH

ICE I

ICE III

Pressure (kbar)

T (K)

ICE II

TM

FIGURE 2: Summary of the pressure dependence of the f

dynamic transition temperature, TL, plotted in the P-T p

Also shown are the homogeneous nucleation temperatur

and the temperature of maximum density line, denoted 

ment indicates that the TL line terminates on the upper e

the TH line. Note that we would like to identify the TL th

dicted liquid-liquid transition line in supercooled water 
Because doped or undoped forms of zirconium oxide can be

tailored to adjust the properties of robust catalyst supports

with respect to surface area stability, porosity, and surface

activity, they have come into increasing use in catalyst systems. As with any technologically important nano-particulate

oxides having high specific surface areas, adsorbed water

exerts a great influence on the surface properties of 

these materials. In particular, surface hydroxyl groups and

undissociated water molecules play an important role in many

reactions over zirconia, such as methanol synthesis and the

isosynthesis reaction of CO/H2/H2O. In automotive catalysis, 

zirconia is an important additive to ceria, which is a catalyst

for the water-gas shift reaction, CO + H2O →CO2 + H2.

In order to elucidate the key dynamics of surface water in nano-powder

oxides, we performed a quasielastic neutron scattering (QENS) study of

the dynamics of surface water on zirconium oxide nano-particles using

the time-of-flight and backscattering neutron spectrometers at the NCNR.

The results are described in terms of the “slow” dynamics of an inner

layer of water, more tightly bound to the oxide surface, and the “fast”

dynamics of a more mobile outer layer. 

The hydration of nano-powder ZrO2 was achieved simply by storing the

sample under ambient conditions. The resulting sample had about two

layers of mobile water molecules on top of the immobile surface hydroxyl

groups. The Disc Chopper Spectrometer (DCS) was used with an incident neutron wavelength of λ = 9.0 Å yielding a resolution of about 

19 μeV full-width at half-maximum (FWHM). This allowed us to access

the dynamics of the outer hydration layer on the time scale of 1 ps to

100 ps. In order to access the longer time scales relevant to the dynamics

of the inner hydration layer, we utilized the High Flux Backscattering

Spectrometer (HFBS). This instrument provides 

0.85 μeV (FWHM) allowing one to probe time-

about 100 ps to 1000 ps.

The significant dynamic range of the DCS exper

the rotational (faster) and translational (slower) 

to the QENS signal. Thus, the spectra were fitte

ing function that incorporated a sum of broader 

Lorentzians averaged over the random orientatio

of the surface of the nano-particles with respect 

Q [1]. The two-dimensionality of the surface dif

itself in a scattering function for the translationa

that is more sharply peaked than is a Lorentzian

The rotational correlation time for the outer layer e

τR = 0.341[ps]×exp(EAR/RT), with the activation e

which is lower than the corresponding EAR = 7.7 

The rotational diffusion at room temperature is slo

2 compared to bulk water, whereas the translation

by a factor of 40. 

The correlation time for the translational diffusion 

layer exhibits an Arrhenius-type temperature depe

energy EAT = 11.4 kJ/mol [1], in contrast with bo

known to be strongly non-Arrhenius [3], and the 

discussed below, which also demonstrates non-Ar

We found that the water molecules of the outer h

two-dimensional jumps at a well-defined, almost 

distance of 4.2 Å to 4.3 Å in the course of a therm

jump diffusion process. We propose that an Arr

dependence of the translational correlation time

observed for the rotational, but not the translati

nent, is due to the fact that the number of hydr

molecules of the outer hydration layer with the 

12
The temperature dependence of the average residence time measured on

HFBS was non-Arrhenius, suggesting that the translational motion of the

water molecules of the inner hydration layer is more complex than surface jump diffusion observed for the molecules of the outer hydration

layer. This is likely because the inner layer molecules form more hydrogen bonds with the nearest neighbors compared to the molecules of the

outer hydration layer. The non-Arrhenius temperature dependence of 

the residence time suggests the presence of a singularity in the dynamics

of the inner hydration layer. Fitting with the Vogel-Fulcher-Tamman

(VFT) law, τ = τ0exp(DT0/(T-T0)), yields the singularity temperature 

T0 = (189 ± 1) K. The quality of the fit is demonstrated in Fig. 1.

Existence of such a singularity indicates the importance of cooperative

effects in the dynamics of the inner hydration layer as opposed to the

outer hydration layer.

FIGURE 1: The temperature dependence of the residence time for the translational diffusion component of “slow” (inner layer) surface water in ZrO2 fitted

with a VFT law, τ = τ0exp(DT0/(T-T0)), and plotted as a function of T0/(T-T0),

with T0 = 189 K.

FIGURE 2: The temperature dependence of the residence 

tional (τT) and rotational (τR) diffusion of surface water 

surface water is interpreted as an inner layer more tightl

and the “fast” water as an outer layer atop the inner one

water (after Teixeira et al. [3]) are shown for comparison

To summarize, our QENS study of surface water in Z

dynamics of “slow” and “fast” hydration water as sho

former was ascribed to the water molecules in direct 

surface hydroxyl groups (that is, the inner hydration 

ter was associated with the water molecules in contac

surface water (that is, the outer hydration layer). At r

the translational dynamics of the outer and inner hyd

slower than that of bulk water by a factor of 40 and 5

compared to that of bulk water, whereas the rotation

surface water is only slightly slower than that of bulk 

REFERENCES

[1] E. Mamontov, J. Chem. Phys. 121, 9087 (2004).

[2] E. Mamontov, J. Chem. Phys., 123 024706 (2005

[3] J. Teixeira, M.-C. Bellisent-Funel, S.-H. Chen, A. J

Rev. A 31, 1913 (1985).

1.0 1.5 2.0 2.5 3.0 3.5 4.0

6.0

6.2

6.4

6.6

6.8

7.0

7.2

res

10

10

10

0

1

2

2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4

-1

[p
Portland cement is the world’s most important construction

material, with annual production currently exceeding 800 million metric tons. The structure, molecular composition, and

physical properties of cement vary immensely during hydration, changing from a material that can be poured and worked

to one that is literally hard as rock. The details of this metamorphosis depend on the structure and composition of the

starting cement, as well as the hydration conditions.

Correlating the original composition and hydration kinetics

with the final properties is the aim of this research. With better understanding of these processes, we improve our ability

to control and design the final product properties. Neutrons

are well suited for the investigation of the structure and reaction mechanisms of cement, as they are particularly sensitive

to hydrogen (and thus water), and are highly penetrating, so

they can sample larger volumes than other methods. This

research reveals complexities of the hydration of cement, 

and suggests ways to exploit these results to improve 

cement performance. 

The initial cement powder is a complex mixture of several calcium silicates, calcium aluminates, calcium alumino-ferrites, as well as other

phases. Tricalcium silicate is the most abundant phase in Portland

cement and is primarily responsible for giving cement its strength in the

crucial first 24 hours of hydration. Thus, its hydration has been extensively

studied. Dicalcium silicate, the second most abundant component, is

much less reactive than tricalcium silicate and as such was not expected

to contribute significantly to the overall hydration in the critical first 

24 hours. Although it was recognized that the hydration of cement involves

the interaction of the different components, very little is known about

combined reactions. In this highlight we report the results of quasielastic

and inelastic neutron scattering (QENS and INS

mixtures of only tricalcium and dicalcium silica

the strengths of mortars of mixtures of these com

QENS data were obtained using the NIST Ferm

neutron spectrometer (FCS). The kinetics of th

characterized using the “Bound Water Index” (B

mined from the ratio of the amount of less mob

relative to the total H in the system. As H is init

water and is transferred to the reaction products 

of tricalcium and dicalcium silicate, the BWI is e

of the amount of product. Thus, a plot of BWI v

the kinetics of the hydration reaction. A typical 

Fig. 1. After an initial dormant period, two hyd

be identified: (a) the nucleation and growth of p

cement starts to set, and (b) diffusion- limited h

the permeability of the reaction products limits t

reach the hydrating particles. 

14

-2 -1 

0.0

2.5

2.0

1.5

1.0

0.5

ω

-2 -1 

0.0

2.5

2.0

1.5

1.0

0.5

0

0.02

0.04

0.06

0.08

0.10

0.12

0 10 20 30 

BWI

data

)

-2 -1 

0.0

2.5

2.0

1.5

1.0

0.5

-2 -1 

0.0

2.5

2.0

1.5

1.0

0.5

-2 -1 

0.0

2.5

2.0

1.5

1.0

0.5

-2 -1 

Hydration time (hours

S (Q, 0.0

2.5

2.0

1.5

1.0

0.5

0.0

2.5

2.0

1.5

1.0

0.5

-2 -1 

model

FIGURE 1: Diffusion models and BWI curve for 

mass fraction of 50 % tricalcium silicate. Errors 

shows a snapshot of QENS data fitting at 5 hou

ing the Gaussian and three Lorentzian profiles u

various states (dotted lines). The solid line indi
Comparison of the BWI curves for various tricalcium and dicalcium silicate mixtures indicates that the reaction at intermediate compositions

cannot be simply described as a linear combination of the end points.

Fitting of the hydration curves to a kinetic model allows this difference in

the hydration to be quantified by extracting several parameters related to

the kinetics. For example, the parameter A can be determined, which

represents the expected BWI after infinite time if the nucleation and

growth mechanics had not been interrupted. A is useful for predicting

early strength development, as the amount of product (as well as type)

correlates with cement strength. Parameter A exhibits a maximum

between 80 and 95 % as a function of the starting mass fraction of tricalcium silicate in the mixture. Figure 2 displays A versus starting tricalcium

silicate mass fraction, along with the effective diffusion constant of water,

Di

, which limits the reaction rate in the diffusion-limited regime. The

trend of Di correlates well with that observed for the parameter A.

Compressive strength (shown inset in Fig. 2) of mortars of these mixtures

after 28 days hydration also correlates with the quasielastic neutron 

scattering results. 

In order to quantify the amount of Ca(OH)2 produced during the 

reaction, INS data were obtained using the NIST filter analyzer neutron

spectrometer (FANS). The amount of Ca(OH)2, an important hydration

product, present at any time during hydration, was determined by 

comparing the intensity of a vibrational mode at 42 meV to one in a 

reference sample of Ca(OH)2. The results displayed in Fig. 3 reveal 

a clear maximum in the amount of Ca(OH)2 produced at a mass 

fraction of 90 % tricalcium silicate.

The quasielastic and inelastic neutron scattering data clearly indicate 

that the reaction products formed during the nucleation and growth

regime for mixtures containing 80 % to 95 % tricalcium silicate differ 

significantly from those produced by other mixtures. Moreover, these

results demonstrate that more products form during early hydration

times in this composition range. This is particularly surprising for 

calcium hydroxide since there is less total Ca in mixtures containing

dicalcium silicate than in tricalcium silicate alone. These results also 

determined from this work of 80 % to 95 % for optim

mechanics, and alarmingly close to the local minimu

mechanics, and strength, between 70 % and 75 %. T

increasing the tricalcium silicate content by 5 % to 1

improved cement. However, there are many other co

clinker and other interactions could also affect the pe

final material. 

FIGURE 3: Amount of Ca(OH)2 produced at 22 hours 

um and dicalcium silicate mixtures, determined by IN

are 1 standard deviation, and in composition are sma

REFERENCES

[1]. V. K. Peterson, D. A. Neumann, R. A. Livingston

(submitted 2005).

[2] V. K. Peterson, D. A. Neumann, R. A. Livingston 

Scattering as Probes of Multiscale Phenomena, ed. S.

Khalifah, D. Pochan, and P. Radaelli (Mater. Res. 

840, Boston, MA, 2004).

Tricalcium Silicate mass fracti

x 10 Moles Ca(OH) 2 -4

0.6 0.7 0.8 0

2

4

6

8

10

0
Polymer solutions and colloidal suspensions are representative

complex fluids. For block copolymers in selective solvents,

microphase separation can lead to the formation of spherical

structures called micelles in which both the polymeric and colloidal nature of the structures figure significantly. For example,

at high concentrations, interactions between micelles become

important and the micelles can undergo order-disorder transitions akin to the crystallization of spherical colloids. However,

because of the polymeric nature of these micelles, the characteristics of this phase behavior are expected to differ considerably from hard-sphere colloids. Similarly, the dynamical behavior

of the micelles within these concentrated phases should reflect

both colloidal and polymeric aspects of the system. We have

conducted a neutron scattering study of concentrated triblock

copolymer micelle solutions that addresses these issues. The

study includes small angle neutron scattering (SANS) to characterize the structure and phase behavior of the micelles and neutron spin echo (NSE) experiments to examine the local dynamics and their dependence on micelle structure and phase.

The micelle-forming copolymer under study is Pluronic, an ABA-type triblock

with outer blocks of polyethylene oxide (PEO) and a central block of polypropylene oxide (PPO). Due to the relative hydrophobicity of PPO, Pluronic in

aqueous solution with appropriate ratios of PPO to PEO forms spherical

micelles over a broad range of concentration and temperature, with PPO cores

and swollen PEO coronas. Our study involves two species of Pluronic, F68

and F108, that have the same PPO to PEO ratio; in each case, the chains have

a mass fraction of 80 % PEO. However, the overall chain length of F108 is

larger than that of F68 by roughly a factor of two. Specifically, the average

molecular weight of F108 is 14 600 g/mol while that of F68 is 8400 g/mol.

Comparing the species provides insight into how the phase behavior and local

dynamics vary with chain length.

FIGURE 1: (a) SANS intensity of 0.21 g/cm3 F108 

temperatures. (b) Schematic pictures of the polyme

SANS. (c) and (d) Phase diagrams for F68 and F1

determined by SANS. Three phases are identified: 

tion (black), micelles with liquid-like order (blue), 

talline order (red).

Figure 1(a) displays the SANS intensity I(Q) for 0.2

several temperatures. Consistent with previous stud

lineshape indicates a sequence of phase transforma

perature starting from a dissolved polymer solution 

proceeding to micelles with liquid-like order, follow

and then finally back to a micelle liquid, as shown 

Phase diagrams constructed from SANS for F108 a

Figs. 1(c) and 1(d), reveal two significant difference

First, the minimum concentration for crystalline or

tion for the shorter-chain F68. Second, the temper

perature micelle liquid region is larger for F68 than 

(approximately 30o C for F68 compared with abou

differences indicate a stabilization of the micelle liq

for the shorter-chain copolymer. We associate this t

length dependent effects observed in highly asymm

melts that microphase separate into spherical dom

liquid-like packing of spheres is often observed ove

range between the disordered phase, in which t

and a crystalline phase.

16
intermediate scattering function S(Q,t)/S(Q,0) of 0.3 g/cm

F68 in D2O meas

ured with NSE in the low-temperature micelle liquid phase at various wave

vectors near and above the interparticle peak in I(Q). The measurements

reveal a strongly Q-dependent lineshape that deviates from a single relaxation.

The inset of Fig. 2(b) shows S(Q,t)/S(Q,0) of 0.21 g/cm3 F108 in the micelle

liquid and crystalline phases. The dynamics are remarkably insensitive to

phase and hence to the local micellar packing. 

To characterize these dynamics more precisely, we have performed additional

measurements on solutions of F68 with deuterated PEO. The deuterated PEO

blocks have a scattering length density that closely matches that of D2O;

hence the hydrogenated PPO in the micelle cores dominates the signal.

Figure 2(b) shows a comparison of the intermediate scattering functions for

F68 solutions with deuterated and hydrogenated PEO in the low-temperature

micelle liquid phase. A stretched-exponential lineshape with stretching exponent near 0.5 describes accurately the intermediate scattering function for the

micelle solutions with deuterated corona at all temperatures and wave vectors,

as illustrated by the solid line in Fig. 2(b). Figure 2(c) displays results for the

correlation time τPPO extracted from such fits in the low-temperature micelle

liquid phase. The solid line through the data is the relation τPPO ~ Q-4. Such

a stretched correlation function with τ ~ Q-4 is a signature of Rouse modes

[3]. Thus, we conclude that NSE captures the segmental chain dynamics of

the PPO in the micelle cores. In particular, translational diffusion is not

observed (see dashed line in Fig. 2(c)) presumably due to slowing by hydrodynamic interactions [4] among the concentrated micelles. 

Armed with these results, we analyze the NSE measurements for the solutions

of fully hydrogenated F68 by assuming that the PPO dynamics are identical to

those determined for the solutions with deuterated PEO. Specifically, we fit the

results for the hydrogenated Pluronic with a two-component lineshape that

includes a term identical to that obtained for the Rouse modes in the core and

a term that is a simple exponential designed to account for the contribution

from the corona. The success of this fitting, illustrated by the dashed line in

Fig. 2(b), implies a clean separation of segmental dynamics between core and

corona. The correlation times for the PEO dynamics, τPEO, extracted from

these fits vary with wave vector as τPEO ~ Q-2, as shown in Fig. 2(c), indicating

that the NSE measurements capture the diffusive motion in the corona. The

corresponding diffusion coefficient matches quantitatively that expected for 

the longitudinal diffusive modes of polymer brush laye

[6,7]. Thus, we interpret that the PEO blocks in the co

cally just like a polymer brush, despite the large curvat

separating core and corona.

In conclusion, this combined SANS and NSE study of Pl

ed several features of polymer micelle solutions. The pha

solutions indicates chain-length dependent composition 

segmental dynamics probed with NSE, however, while s

microphase separated micellar environment, remain larg

micellar phase behavior. 

REFERENCES

[1] R. K. Prud’homme, G. Wu, D. K. Schneider, Langmu

[2] J. Wang, Z.-G. Wang, Y. Yang, Macromolecules 38

[3] B. Ewen, D. Richter, Adv. Polym. Sci. 134, 1 (199

[4] P. N. Segré, P. N. Pusey, Phys. Rev. Lett. 77, 771 (

[5] Z. Zhou, B. Chu, J. Colloid Interface Sci. 126, 17

[6] P. G. de Gennes, Adv. Colloid Interface Sci. 27, 1

[7] G. E. Yakubov et al., Phys. Rev. Lett. 92, 115501 

FIGURE 2: (a) The intermediate scattering function m

tron spin echo for 0.30 g/cm3 F68 at 30o C in the low

micelle liquid phase at several wave vectors. (b) The 

ing function at Q = 0.12 Å-1 for fully hydrogenated F

F68 with deuterated PEO blocks (blue) in the low-te

liquid phase. The solid line is the result of a fit to a s

form. The dashed line is the result of a fit to the sum 

and a stretched exponential. The inset to (b) shows a 

intermediate scattering functions for 0.21 g/cm3 F10

uid (purple) and micelle crystal (orange) phases. (c) 

relaxation times for dynamics in the PPO core (blue) 

(green) of 0.30 g/cm3 F68 in the micelle liquid phas

the relation τ PPO ~ Q-4 expected for Rouse modes. τ 

τ PEO ~ Q-2 expected for longitudinal diffusion mode

brush. The dashed line shows translational diffusion 

extrapolation of the behavior in dilute suspensions [5
Wormlike micellar solutions formed by self-assembled surfactants exhibit rheological properties such as shear thinning

and suppression of turbulent flow that are related to the flowinduced changes in their structural conformations or orientations. These flow properties are of relevance in such applications as thickeners, drag reducers and flow improvers in the

food and cosmetics industries.

In this highlight we report measurements of the microstructure of a

shear-induced phase separating (SIPS) wormlike micellar solution by 

performing small angle neutron scattering (SANS) measurement using a

novel shear cell capable of gap-resolved measurement in the 1-2 (velocity

velocity-gradient) plane. Quantitative results show evidence for shearinduced microphase separation accompanied by shear banding. The

results suggest that both concentration fluctuations and gradients in 

segmental alignment occur during SIPS.

The nonlinear rheological behavior of complex fluids includes rich phenomena such as shear-induced phase separation (SIPS). Although many

polymeric and self-assembled systems show a wide variety of related 

phenomena, self-assembled solutions of surfactants forming wormlike

micelles [1] have proven to be especially robust in exhibiting clear signatures of SIPS and as such, are of significant scientific interest [2–4]. A

rheological signature of SIPS in wormlike micelles is a stress plateau.

Models suggest this corresponds to a multi-phase flow regime composed

of a low shear micellar solution and a high-shear, highly aligned wormlike fluid state. While global rheological response is important in characterizing these wormlike micellar solutions, local velocity and concentration profiles provide a greater understanding of the phase separation/

shear banding phenomena.

A variety of techniques, employed in previous studies, such as dynamic

light scattering and NMR, have provided local velocity profiles of the 

shear-banded state. More recently, particle-track

vided spatial and temporal information. Howeve

tion provided about the microstructure of the h

optical turbidity. Therefore, SANS investigations 

great value, especially a combination of studies 

the flow field, i.e., the flow-vorticity (radial beam 

gradient-vorticity (tangential configuration), and t

(1-2 plane) planes.

Small angle neutron scattering patterns collected 

employed a newly designed aluminum Couette 

2 mm gap and 10 mm path length) that is illust

preceding the cell reduced the neutron beam to 

2.0 mm in height. The center of the narrowed b

18

-2 -1 0 1 2 3

0.0

0.2

0.4

0.6

0.8

1.0

Tr

 Position [mm]

 Tr (exp)

 Tr (calc)

 

1

3

2

CCW

FIGURE 1: Illustration of the 1-2 plane shear cell in 

for gap-resolved studies. The graph shows the reco

mission as a function of beam position along the 2 
at 0.5 mm, 1 mm and 1.5 mm from the inner (rotating) wall. A stepper

motor could attain shear rates from 0.1 s-1 to 100 s-1, where positive

shear rates correspond to rotation of the inner cylinder in a counterclockwise sense, looking through the cell toward the detector.

Figure 2 shows data recorded in all three planes of the flow field. The

“radial” and “tangential” data were recorded in a conventional Couette

cell with the rotation axis perpendicular to the beam. The radial scattering

pattern displays a clear anisotropy along the vorticity axis while the tangential beam is isotropic. Hence the micelles are aligned parallel to the flow

axis. The data from the 1-2 plane clearly demonstrate that micelles orient

with a finite angle (between 0° and 45°) to the flow axis, and flow reversals

demonstrate that this orientation changes sign, as expected. Note that data

from the 1-2 plane are required to quantify both the degree and the angle

of alignment. Indeed, the 1-2 plane SANS results are in quantitative agreement with independent flow birefringence measurements.

Segmental alignment factors A f , are calculated from the scattering patterns, where – 1 < A f < 0 with 0 isotropic and -1 flow-aligned. As

shown in Fig. 2, good agreement is observed for the alignment from 

both rheo-SANS devices, further validating the new 1-2 plane flow cell.

However, the gap-resolved 1-2 plane data reveal important new information concerning the micellar structure in the shear banding state. Namely,

there is increasing alignment closer to the rotating wall of the shear cell.

This is expected as independent flow velocimetry measurements indicate

that the shear rate is higher near the inner cylinder as a consequence of

the flow kinematics and the shear thinning properties of the micelle solutions [5]. As nominal shear rates in the stress plateau region are probed,

distinct bands form. The outer band has a shear rate of approximately 

10 s-1 to 20 s-1. An inner band exhibiting velocity fluctuations has shear

of a sharp interface and corresponds to fluctuations i

density on length scales longer than the entanglemen

wormlike micellar network, i.e., microphase separate

observed on these length scales in accordance with th

of optical turbidity at high shear rates.

This study provides new evidence linking shear band

micellar solutions to a shear-induced phase separatio

of these patterns is being undertaken to resolve the m

changes during SIPS. 

Funding from Unilever and the Alexander von Humb

gratefully acknowledged.

REFERENCES

[1] H. Rehage and H. Hoffmann, Mol. Phys. 74, 933 

[2] M. E. Cates, J. Phys.-Condens. Mat. 8, 9167 (199

[4] Y. T. Hu and A. Lips, J. Rheol., submitted.

[5] M. W. Liberatore, F. Nettesheim, L. Porcar and N. 

Rev. Lett., submitted.

FIGURE 2: Scattering from 40mM EHAC and 300mM NaSal. Top: Scattering

images from the 1-2 plane at shear rates 0, -32 s-1, +32 s-1 and +75 s-1 from

left to right. Left: Radial and tangential beam scattering images at 32 s-1.

Bottom right: Alignment factors of the radial and 1-2 plane experiments as 

a function of shear rate. Alignment Af proceeds from zero at rest toward flow

alignment at -1 with increasing shear rate. Beam position within the gap in

the 1-2 plane is coded by color.

101

102

103

10-2 101

102

103

shear rate = 3.2 s-1

10° sector parallel to 

the nematic director

I(q) / cm-1

q -1

sh

1

th

shear rate = 3.2 s-1

10° sector perpendicular

to the nematic director

shear 

10° s

to the 

q / Å-1

q -1

q -4

q -1

q -4

q -1

FIGURE 2: Radial intensity distributions in the zero shea

the shear-thinning regime (right) at three different gap p

perpendicular to the primary axis of micellar orientation

corresponds to the onset of turbidity at high shear rates.
Thin polymer films are finding increasing use as coatings in a 

variety of settings, including the electronics industry. Fine-tuning 

of surface properties for these uses, as well as fine tuning of 

processing behavior, can be accomplished by blending polymers 

of different architectures, e.g., linear and branched. In this highlight

we consider blends in which model polymers of well-defined architecture are used. In general, the composition of an interface of a

polymer binary blend film differs from the composition of the bulk

because one component is preferred at the interface [1]. Neutron

reflectometry (NR) measurements of interfacial segregation in

architecturally asymmetric blends of long-branched and linear 

polystyrene chains allow separation of the influence of the number

of chain ends from the influence of the number of node points on

interfacial segregation. Complementing the NR measurements

with Surface-Enhanced Raman Spectrometry (SERS) measurements strengthens the analysis. 

Key to the study was the design and anionic synthesis of two groups of

novel, well-defined, highly branched polystyrenes (PS) shown in Fig. 1 [2].

In group I the number of node points in a molecule was varied from 1 to 2

to 4 while the number of ends (branches) was fixed at 6. In group II the

number of node points in each molecule was fixed at 4 and the number of

ends varied among 6, 9, and 13. 

The polydispersities for all polymers were below 1.05 and the overall molecular weight of each polymer was controlled to be about 36 kg/mol to exclude

the possibility that interfacial segregation could be driven by molecular weight

differences [2]. Films of approximately 950 Å thickness with a 20 % volume

fraction branched h-PS, blended with d-PS (36 kg/mol), were spun cast from

solution directly onto clean silicon wafers from which the native oxide had

been etched using HF solution. The samples were annealed in high vacuum at

180  ̊C for 12 h and NR measurements performed on the NG-1 reflectometer. 

FIGURE 1: Structures of the branched polystyrenes and 

group I the number of branches is fixed at 6 and the n

from 1 to 4. In group II the number of branches is va

number of node points fixed at 4.

Concentration depth profiles of the films were infer

fitting a model depth profile to the experimental re

analysis for the blend with the 6-pom chain is show

tion depth profile (inset in Fig. 2) from fitting the N

tial segregation of the pom-pom molecule at both t

interfaces. This was observed despite the fact that t

segregation of the deuterated linear material to the 

The strength of the interfacial segregation for the di

summarized in Table 1 by reporting the interfacial 

Γ = ∫ [ø (z) – øc]dz, where ø(z) is the volume fract

component at a depth z for the annealed sample an

concentration in the center of the film, zc. The resu

ear isotopes quantify the magnitude of the driving 

the isotopic difference alone. The linear d-PS was e

depleted at the substrate interface. Notwithstanding 

of linear d-PS with branched h-PS, the driving force 

architectural differences is strong enough that the c

branched component was enriched at both film inte

surface increased monotonically, but slowly, with th

among the blends in which the number of chain en

20

GROUP I

zc

0

6-star 6-pom 

6-branched 9-branched 

GROUP II
The excess at the substrate interface behaved quite differently, being roughly

twice that at the surface for the blends containing the star and the 6-branch

chains, but smaller for the blend containing the 6-pom chain. Both the isotopic effect and architecture effects drive the branched chain to the substrate

interface, while at the air surface one driving force counteracts the other. 

For the group of three samples in which the number of node points is held

constant at 4, the surface excess increases sharply with the number of chain

ends, while the excess at the substrate varies little. This observation is consistent with the contention that the number of chain ends plays a bigger role at

the substrate interface for which the chemistry of the chain ends is more

important. Due to the manner in which in the chains were synthesized, the

ends all have butyl initiator fragments and the surface energy of those end

groups is somewhat lower than that of a styrene repeat unit. The general 

overall impression is that the number of node points and precise topology

play bigger roles at the substrate interface than at the air interface (surface).

The number of chain ends is more important at the air surface than at the

substrate interface. 

FIGURE 3: Comparison of the variation in surface compo

of node points and number of chain ends in the hydroge

the blend for unannealed samples measured with NR (op

annealed samples measured with NR (circles), and annea

ured with SERS (triangles).

In summary, complementary NR and SERS measurem

segregation at the surface and substrate interface of b

well-defined branched polystyrenes demonstrate una

the strength of the segregation is not simply a functio

chain ends, but rather is sensitive to the details of the 

are currently pursuing a comparison of the experime

theory of Wu and Fredrickson [5].

This research was supported by The American Chemical 

Research Fund (#38915-AC7), an Ohio Board of Regent

the Collaborative Center for Polymer Photonics, which is 

UA, AFRL, and AFOSR.

REFERENCES:

[1] R. A. L. Jones, E. J. Kramer, M. H. Rafailovich, J. Sok

Phys. Rev. Lett. 62 (3), 280 (1989).

[2] J. S. Lee, R. P. Quirk, M. D. Foster, Macromolecules 3

[3] P. P. Hong, F. J. Boerio, S. D. Smith, Macromolecules 

[4] Y. W. Alsmeyer, R. L. McCreery, Anal. Chem. 63 (13)

[5] D. Wu, G. Fredrickson, Macromolecules 29 (24), 79

01234

10

20

30

40

50

60

70

80

90

h-PS Near Surface 

Concentration (vol %)

No. of Node Points

 Before Annealing

 NR 

 SERS 

2 4 

 Before A

 NR 

 SERS 

FIGURE 2: Neutron Reflectivity, R, as a function of scattering wavevector, q, 

for a blend of 20 % volume fraction of 6-pom h-PS with linear d-PS spun cast

onto a Si wafer and annealed for 12 h at 180oC. The solid line in the main

graph represents the reflectivity calculated from the model concentration depth

profile shown in the inset (note pom-pom concentration at interfaces.)

TABLE 1: Surface and interface excesses of the hydrogenous component in

annealed blend films determined by NR

Blend Surface Excessa (Å) Interface Excessa (Å)

Linear h-PS/d-PS -2 5

6-star h-PS/d-PS 6 15

6-pom h-PS/d-PS 8 12

6-branch h-PS/d-PS 11 19

9-branch h-PS/d-PS 22 28

13-branch h-PS/d-PS 38 29

aThe uncertainties are ±1 Å.
The interaction of proteins with membranes is an important

part of many cellular processes, but is poorly understood

partly due to the difficulty of producing a biomimetic environment that is suited to comprehensive measurement. Solidsupported lipid membranes provide robust systems, which

can be studied using several complementary techniques,

including neutron reflectometry – a technique that provides

structural information in the sub-molecular size range. Our

work, using the CNBT Advanced Neutron Diffractometer /

Reflectometer (AND/R), has focused on the optimization and

characterization of model systems for the reconstitution of

pore-forming membrane proteins. We have produced a synthetically straightforward bilayer membrane system, which is

tethered above a gold-substrate and contains a sub-membrane solvent reservoir that is now beginning to be used to

probe the details of membrane-active proteins.

Membrane proteins, i.e., proteins that interact with cell membranes or are

integral parts of membranes, play an essential part in mediating the relationship between a cell and its surroundings, and display a rich variety of

structures and functions. However, a cell membrane is an intrinsically

highly disordered system, which relies on this disorder for its physiological functioning, and thus is not well suited to crystallography studies.

Furthermore only a small number of membrane-integral proteins have

been crystallized and this number is growing much more slowly than for

soluble proteins [1]. Solid support allows membranes to be investigated

by AFM, ellipsometry, neutron reflectometry, and electrochemical methods including electrical impedance spectroscopy (EIS). These membranes are then a more biologically relevant surrounding in which proteins can be incorporated to gain structure and function information.

The solid support also makes systems robust, which enables the development of biosensor applications.

The tethered membrane systems in this work ar

(WC14) synthesized at NIST, in which the two 

though a glycerol to a thiolated hexa(ethylene o

er supports the membrane above a gold surface

for a sub-membrane solvent reservoir. This is n

membrane proteins to extend beyond the memb

the effects of the solid surface on the membrane

AND/R, supported by EIS, show that complete m

formed on these tethers using an adaptation of t

exchange” method developed by Cornell et al. [

22

-1

0

1

2

3

4

5

6

7

0 10 20 30 40 50 

Distance from interface [Å]

Scattering Length Density [10 Å ] -6

(b)

30 % WC14

50 % WC14

100 % WC

-2

WC14

(a)

FIGURE 1: a) A cartoon of the surface-supported l

of the artificial lipid WC14 spaced-out on the surfa

cules. b) Scattering length density profiles derived 

show the decreasing amount of WC14 on the surfa

the SAM-forming solution decreases, with the colla

sparsely-tethered systems.
means that more traditional vesicle-rupture techniques have proven

unfruitful. However, using solvent exchange with a variety of completing

lipids produces bilayer membranes that EIS shows are electrically sealing,

with low capacitance and conductivity. Importantly, we can determine

uniquely from the AND/R measurements that there is a distinct hydrated

reservoir of about 20 Å under a sparsely-tethered membrane (Fig. 2) [3]. 

FIGURE 2: (a) AND/R reflectometry measurements on a system made from a

50 % mixture of WC14 and the βME, show that there is water in the WC14

sub-membrane space (shaded in blue) revealed in the changes of the derived

SLD profile (b) for the two contrasts.

The membranes produced have been challenged by a membrane-active

phospholipase protein, PLA2. The protein, found in environments as

diverse as livers and bee venom, cleaves the acyl-ester bond in the sn-2

position of glycerophospholipids, eventually destabilizing and destroying

naturally occurring lipid membranes. PLA is known to be sensitive to the

small-scale lateral structure of the membrane, and can therefore be used

FIGURE 3: Electrical impedance spectroscopy (EIS) capa

ments showing the reaction of a bilayer formed from DO

mixture of 70:30 βME:WC14 to a solution of PLA2.

The tethered bilayer membranes that we have develo

and optimized show exciting potential as tools to stu

function relationships of membrane proteins. Carefu

preparation conditions allows us to produce bilayer m

mimic a fully hydrated natural membrane, but which 

amenable to measurement with many different techn

possibility of their development as biosensor templat

This work was supported by the National Science Fo

grant #0304062. The CNBT and AND/R are supporte

Institutes of Health under grant #1 R01 RR14812 an

the University of California.

REFERENCES

[1] S. H. White, Protein Science 13, 1948 (2004).

[2] B. A. Cornell et al., Nature 387, 580 (1997).

[3] Submitted to JACS.

[4] K. Jørgensen, J. Davidsen, O. G. Mouritsen, FEBS 

23 (2002).

[5] Submitted to Langmuir.

-8

-7

-6

-5

-4

-3

-2

-1

 0

0.01 0.03 0.05 0.07 0.09 0.11 0.13 0.15 0.17 0.19

Momentum Transfer Q Z [Å ] -1

Reflectivity 10

10

10

10

10

10

10

10

10

(a)

-1

0

1

2

3

4

5

6

7

-10 0 10 20 30 40 50 60 70 80

Distance from interface [Å]

Scattering Length Density [10 ] -6Å-2

Gold WC14 DPhPC Water

D O

H O: D O

2

2 2

D O2

H O: D O 2 2

(b)

0.0

0.5

1.0

1.5

2.0

0 50 100 150 200 250 

Time [min]

te

etha

rins

PLA2 injection

Ca2+ addition

DPhPC

POPC

Capacitance @ 1033 Hz [ F]
The essential role of highly unsaturated fatty acids for human

health, in particular for brain development and function, has

been well established [1]. The membranes of brain synapses

and of the retina may contain up to 50 mol % docosahexaenoic acid (DHA, 22:6n3) as hydrocarbon chains. DHA is

a polyunsaturated, ω-3 fatty acid with 22 carbons and six double bonds. Reconstitution experiments with rhodopsin have

shown that high concentrations of DHA are essential to

achieve levels of rhodopsin activation by light that are similar

to levels in rod outer segment disk membranes of the retina

[2]. The efficiency of GTP-binding protein (G-protein) coupling

to the photoactivated rhodopsin depends on membrane DHA

content as well [3]. Rhodopsin belongs to the family of G-protein coupled membrane receptors (GPCR) that transmit extracellular signals elicited by compounds like neural transmitters,

hormones, odorants, or light to the interior of cells where they

activate G-proteins. This large superfamily of heptahelical

receptors comprises receptors for dopamine, serotonin, 

epinephrine, opioids, and cannabinoids, just to mention a few. It is

likely that other synaptosomal GPCR have a specific requirement

for high concentrations of DHA for proper function as well. 

FIGURE 1: Snapshot from an MD simulation of rhod

18:0-22:6n3-PC (phosphatidylcholine) bilayer [4]. 

given as a ribbon representation while two DHA ch

The mechanisms by which polyunsaturated lipi

biological function at the molecular level are no

attention. Recent data from NMR, x-ray diffracti

lations studies on polyunsaturated lipids indicat

chains themselves are exceptionally flexible and 

formational transitions [5]. This is contrary to th

past that polyunsaturated hydrocarbon chains p

ties because of their bulkiness and rigidity. One 

polyunsaturated hydrocarbon chains alter memb

that are critical for protein activation by ligands

membranes rich in polyunsaturated lipids are u

ture elastic stress that is partially released when 

changes its shape upon activation. The curvature 

24
molecules per lipid. 

FIGURE 2a: Diffraction data of 18:0-22:6-PC oriented multilayers, with protonated hydrocarbon chains (black), with deuterated stearoyl chains (red), or

with deuterated DHA chains (blue).

By a Fourier synthesis of the coherent diffraction signal in reciprocal

space, the density profiles of saturated 18:0 and polyunsaturated 

22:6 chains, in projection along the normal of the bilayer, as well as the

water distribution were determined (Fig. 2b). The results show clearly

that the chain density of the polyunsaturated DHA (blue trace) extends

further into the lipid water interface. Also, DHA density is higher near

the interface than in the bilayer center. In contrast, the density of saturated chain segments is higher in the bilayer center. Such uneven distribution of chain densities is likely to alter the lateral pressure profile of bilayers that has been linked to changes in the GPCR free energy upon conversion to the activated state [7]. It is important to mention that the

experiments above were conducted in the biologically relevant liquidcrystalline state of lipid bilayers.

Neutron diffraction proves itself as an increasingly important method for

structural investigations of biological matter. Advancements in neutron

techniques, combined with the increased availability of specifically 

deuterated biological material, enable structural studi

level with unprecedented resolution. The power of n

studies unfolds particularly well if the results are com

scopic approaches like NMR and molecular simulatio

this project.

ACKNOWLEDGMENTS

The AND/R, constructed by the Cold Neutrons for Bi

Technology (CNBT) partnership, is supported by the 

of Health under grant #1 R01 RR14812 and by The R

University of California.

REFERENCES:

[1] N. Salem, Jr., B. J. Litman, H. Y. Kim, and K. Gaw

Lipids 36, 945 (2001).

[2] B.J. Litman, S. L. Niu, A. Polozova, and D.C. Mitc

Neurosci. 16, 237 (2001).

[3] S. L. Niu, D. C. Mitchell, S. Y. Lim, Z. M. Wen, H

N. Salem, Jr. and B. J. Litman, J. Biol. Chem. 279

[4] S. E. Feller, K. Gawrisch, T. B. Woolf, J. Am. Chem

4434 (2003).

[5] N. V. Eldho, S. E. Feller, S. Tristram-Nagle, I. V. P

and K. Gawrisch, J. Am. Chem. Soc. 125, 6409 (

[6] http://www.ncnr.nist.gov/programs/reflect/ANDR

[7] R. S. Cantor, Biophys. J. 76, 2625 (1999).

[8] M. C. Wiener, and S. H. White, Biophys. J. 59, 1

0 0.2 0.4 0.6 0.8 1

100

101

102

103

104

18:022:6 PC

18:022:6(d11) PC

18:0(d35)22:6 PC

Q [Å ]

z

-1

Reflected Intensity

FIGURE 2b: The individual chain and water distributions 

66 % relative humidity. The density profiles, shown here w

bands, are on an absolute scale [8] up to a multiplicative 

accounting for the area per lipid.
The pharmaceutical industry increasingly depends on the 

ability to store proteins without degradation, and relies on

increasing understanding of protein function in the design of

medications. Using an approach combining neutron spectroscopy with molecular dynamics simulations, we highlight

recent results addressing these issues by characterizing protein dynamics via their non-exchangeable protons. In particular, the dynamics of methyl group protons is distinct and

apparently separable from other aliphatic protons, and

because methyl groups are numerous and strategically distributed they can be used as a powerful probe of protein

structure and function. Regarding stability, the onset of anharmonic behavior is found to depend on the level of hydration.

We have also found both a lower temperature hydration-independent activation regime, and a higher temperature hydration-dependent regime that is directly related to the onset of

biological activity in enzymes.

Proteins are ubiquitous high molecular weight heterogeneous polymers

that, beside their obvious importance in nature, are now a major fraction

of all drugs manufactured in the world [1]. Only a few techniques exist

that can even crudely probe protein structure and dynamics in the amorphous state. Fortunately, neutron scattering is proving to be a powerful

method to quantitatively measure proteins in native and non-native environments. Molecular dynamics computer simulations, when carried out in

concert with high-resolution neutron scattering experiments, can provide a

detailed microscopic interpretation to macroscopic observables. This is

possible since both time (fs to ns) and length (Å to nm) scales of computer

simulation and neutron spectroscopy overlap thus allowing for the validation of simulation methodologies and force field parameters. We are applying a combined experimental and computational effort to understand the

factors leading to the activation of dynamical modes in proteins. 

As the temperature is raised above about 200 K

undergo a change in dynamics, the so-called dy

glasslike, in which the motion is primarily vibra

which transitions between taxonomic substates 

to which the solvent affects protein dynamics ha

mental studies aimed at elucidating the role of s

protein function and their practical application 

maintenance of protein function and suppressio

ways. We have studied the role of hydration on 

groups in the protein ribonuclease A (RNase), in 

dehydrated powders via validated molecular dyn

temperature dependence of the mean square flu

vidual methyl groups in a hydrated RNase and d

is shown in Fig. 1. In the hydrated system, the 

linearly with temperature below the dynamical 

approximately 200 K, and a majority show an a

perature above 200 K. In contrast, in the dehyd

26

FIGURE 1: MSFs of methyl protons from MD simu

plotted separately for each methyl group: (A) hyd

(B) dehydrated (powder). The thick red lines are 

the crystal structure with methyl groups colored b

300 K (> 1.4 Å2, red; 0.7-1.4 Å2, green; < 0.7 Å2, 
generally follow a roughly linear increase over the entire temperature

range and, on average, do not undergo a dynamical transition. As shown

in the inset of Fig. 1, we find that the dynamical transition exhibited by

the methyl groups occurs throughout the hydrated protein at roughly the

same temperature (about 200 K for most methyl groups), albeit with a

slight dependence on sequence but not on solvent accessibility. The 

transition is suppressed throughout most of the protein in the absence of

solvent. Our study provides direct evidence that both the amplitudes and

distribution of motion above 200 K are influenced by solvent and are not

exclusively an intrinsic property of the protein.

We have studied the hydration dependence of the dynamics of nonexchangeable protons in the protein lysozyme over a wider temperature

range by elastic and inelastic neutron scattering using the High Flux

Backscattering Spectrometer (HFBS) at NIST. In this study we have 

found two temperature regions where the onset of anharmonicity in the

dynamics occurs as shown in Fig. 2. The first occurs at low temperature,

approximately 100 K, and is not dependent on hydration level. Through

analysis of the experimental data and characterization by moleculear

dynamics simulations we have found that the low temperature anharmonicity is dominated by methyl group protons (Fig. 2B). The second,

well-known, dynamical transition at about 200 K appears only in samples with a hydration level (h) greater than 0.2 grams water per gram 

of protein (h > 0.2). After correcting for methyl group contributions, 

Since methyl protons comprise a significant fraction 

protons in proteins (e.g. 26 % in lysozyme) and the p

dynamics appear to be separable from other non-exc

they are a unique atomic probe of protein relaxation 

dynamical modes. In addition to the discrimination o

groups in the secondary relaxation processes as discu

found by simulation studies of lysozyme that the atom

at the low-temperature onset of anharmonicty (appro

all directly adjacent to the active site of the protein. T

vated process could be a general property of enzymes 

inherent and required flexibility of atoms in the func

region of the biomolecule. We are continuing our effo

deuteration both in simulations and in the future exp

the connection between specific dynamical motions a

The inherent dynamical character of methyl dynamic

could also be used to elucidate minor structural chan

formulations of protein pharmaceuticals.

REFERENCES

[1] C. J. Roberts and P. G. Debenedetti, AIChE J. 48, 

[2] J. E. Curtis, M. Tarek, and D. J. Tobias, J. Am. Ch

15928 (2004).

[3] J. H. Roh, V. N. Novikov, R. B. Gregory, J. E. Curt

and A. P. Sokolov, Phys. Rev. Lett. 95, 038101 (20

0 50 100 150

0.0

0.1

0.2

200

Temperature (K)

FIGURE 2: Mean square displacement (<x2>) versus temperature for lysozyme

at various hydration levels (h:  0.05; ● 0.18; ▲ 0.29; ▼ 0.45) measured

using the HFBS. The inset shows low temperature onset of anharmonicity at

temperatures between 100 K to 120 K. (B) Simulated <x2> for all nonexchangeable protons, methyl protons and non-methyl protons in dehydrated

lysozyme. Harmonic behavior is shown as a linear extrapolation from low-temperature data for all protons (solid line) and for methyl protons (dashed line).

Mobile F

0.0

0.0 0.2 0.4 0.6 0.8

100

101

102

0.1

Hydration level, h 

Rate (v [1/s * 10 ]) -6

0

B
The emiT experiment tests time-reversal symmetry in the

beta decay of polarized free neutrons by searching for the

time-reversal-odd, parity-even triple correlation between the

neutron spin and momenta of both the electron and proton.

The detection of this correlation above the small calculable

effect due to final state interactions would be a direct indication of time-reversal symmetry violation. A highly successful

second run of the emiT experiment was recently completed at

the NIST Center for Neutron Research. Analysis of this greatly

improved data set is currently in progress.

Charge-parity symmetry violation (CP violation) beyond that incorporated

within the Standard Model of particle physics is a natural outcome of

attempts to explain the dominance of matter over anti-matter in the universe. Surprisingly, no such violation has yet been observed. CP and timereversal (T) violation can be related to each other through the charge-paritytime (CPT) theorem, so that tests of direct T violation should also help to

illuminate this puzzle. Experimental limits on both neutron and atomic electric dipole moments (T-violating) place strict constraints on some, but not

all, possible sources of new CP violation. Tests of nuclear beta decay, and

neutron decay in particular, complement these EDM experiments. Some

theoretical models that extend the Standard Model, such as left-right symmetric theories, lepto-quarks, and certain exotic fermions could cause

observable effects that are as large as the present experimental limits [1].

The decay probability distribution for neutron beta decay dW, written in

terms of the neutron spin direction σn and the momenta (energy) of the

electron pe (Ee) and antineutrino pν (Eν) was first described by Jackson,

Trieman, and Wyld in 1957 [2].

The triple correlation D is T-odd. A non-zero value 

calculable final state interactions implies a violation 

The most sensitive measurement of D in 19Ne deca

only about a factor of three above electromagnetic 

most recent measurements of D in neutron decay, (

(-6 ± 13) × 10-4 come from the TRINE collaboratio

emiT experiment respectively [4,5]. Standard Model 

tron system are estimated to be approximately 1.3 × 

tivity of current experiments [6]. Recently, using an e

tor, the emiT collaboration completed a second, mor

The emiT detector consists of an octagonal array o

proton detectors concentric to a beam of longitud

The proton detectors are arrays of solid state diod

detectors are rectangular slabs of plastic scintillato

tion is shown schematically in Fig. 1. Decays are d

between an electron and a proton. Because the pr

750 eV, it is much slower than the electron, and a 

be used to reject most backgrounds. This is show

Monte Carlo evaluation of various detector arrange

geometry that is simultaneously optimized for sens

and insensitivity to most systematic effects. The hig

mented arrangement allows for the approximate ca

effects stemming from detector efficiency and solid 

from beam and polarization misalignment. Additio

28

dW ∝ 1 + a ——— + A ——— + B ——— + D ————— dEe dΩe dΩν .

pe • pν

Ee Eν

σn • pe

Ee

σn • pν

Eν

σn • pe ×pν

Ee Eν

Beta Detector Area

Proton Detector Area

(2 x 8 Array)

50 cm

32 cm

n

Neutron 

8.4 cm

FIGURE 1: Schematic diagram of the emiT detecto
y g pg 

measurement. Consequently, the emiT experiment is performed by 

periodically reversing the polarity of the neutron spin and then comparing

the number of coincidence events with opposite signs of the triple correlation

in otherwise identical coincidence pairs of proton and electron detectors.

Using this approach, one can construct a ratio of the number of coincidence

events in which all the factors in the numerator favor events with one sign of

the triple correlation and those in the denominator favor the opposite sign.

For example, the ratio for the geometry shown in Fig. 1 would be,

where the N’s are the number of events seen in the indicated detector

pair. Each factor can be written as, 

N() eipj = C() Ω() ei Ω() pj ε() ej ε() pj ε() eipj (1±K•PD),

where C is proportional to beam fluence in the indicated polarization, the Ω

are the relevant solid angles, the ε are the individual detector efficiencies, and

εep is the correlated portion of the detection efficiency. K is an instrumental

constant determined using a Monte Carlo simulation (note that it multiplies D

and therefore cannot lead to a false effect), and P is the polarization vector.

From the equations one can see that the individual detector efficiencies and

solid angles cancel in R and it is straightforward to solve for D.

While the correlated detection efficiencies nearly cancel, precise alignment of the beam axis, the detector axis, and the magnetic field is critical

to minimizing systematic effects stemming from this term. A misalignment between the detector axis and the neutron spin axis, for example,

can mimic a time-reversal violating signal if the beam is not centered 

in the detector. This false signal (henceforth called the Asymmetric

Transverse Polarization (ATP) effect) is due to a combination of the beta

and neutrino asymmetries (A and B), solid angle, and decay kinematics.

To reduce systematic effects to acceptable levels, both the detector and

the field are aligned to the beam line to within a few milliradians.

The ATP effect is considered to be the largest systematic uncertainty in

the experiment. Other systematic effects, such as variations in flux, polarization, and spin flip frequency (even in the case that they are dependent

on the state of the spin-flipper), can be shown to produce an asymmetry

rotated to point directly at one of the proton detector

oscillation in the number of coincidence events observ

proton detector because of the A and B correlations (

electron is anti-correlated with the neutron spin). By 

the ATP effect in this situation and scaling down to th

alignment, one can obtain a very good estimate of this 

ty. Finally, it is possible to use the data itself as a magne

ing this oscillation as a function of detector number for 

can, in effect, measure the misalignment of the magneti

ured misalignment can be used to scale the ATP runs a

the size of the ATP effect. Initial estimates indicate that 

the order of 2 × 10-5, well below the statistical sensitivi

We have presented a brief overview of the second run of 

Further details can be found in Ref. 7. The improvement

tus after the first run (in particular to the proton detectio

acquisition system) were very successful. As a result, nea

coincident events were collected in a similar amount of r

were more data collected, but they were of much higher 

to noise was improved from about 2.5-to-1 to approxim

In addition, a more thorough characterization of all the s

ties was carried out. We have shown that the largest of th

1 × 10-4, which is below our expected statistical sensitiv

sensitivity is reached, this measurement will be the most 

reversal invariance in beta decay to date. If the analysis y

it will be an unambiguous sign of physics beyond the St

REFERENCES

[1] P. Herczeg, in Proc. of the 6th Int. PASCOS-98, W

Singapore, (1998).

[2] J. D. Jackson, S. B. Treiman, and H. W. Wyld,Jr., Phys. 

[3] F. P. Calaprice, Hyperfine Interactions, 22, 83, (19

[4] T. Soldner et al, Phys. Lett. B, 581, 49 (2004).

[5] L. J. Lising et al., Phys. Rev. C, 62, 055501 (2000

[6] C. G. Callan and S. B. Treiman, Phys. Rev. 162, 1

[7] H. P. Mumm et al., Rev. Sci. Instrum. 75, 5343 (2

R = ,

N

e1p3 Ne2p4 Ne3p1 Ne1p3 Ne1p2 Ne2p3 Ne3p4 Ne4p1 

N

e1p2 Ne2p3 Ne3p4 Ne4p1 Ne1p3 Ne2p4 Ne3p1 Ne1p3 
Exchange biasing has been widely studied in ferromagnetic/

antiferromagnetic (FM/AFM) bilayers [1] and is essential for

the operation of magneto-electronic devices, such as read

heads in computer hard drives. This phenomenon is characterized by a shift of the magnetic hysteresis loop by an

amount known as the exchange field, HE, after field cooling. 

In some systems it has been shown that the exchange coupling at the interface is antiferromagnetic and that HE can

change from positive to negative values depending on the

magnitude of the cooling field [2]. Theoretical models for this

behavior predict the formation of domain walls in either the

FM or AFM layer [1,2]. Here we describe a system in which

exchange bias is the direct result of a frozen interface domain

wall, revealed by polarized neutron reflectivity (PNR), whose

width depends on the cooling field.

GdFe/TbFe ferrimagnetic bilayers are ideal for studying magnetic 

configurations in exchange-biased bilayers [3] because their magnetic

behavior mimics that of typical FM/AFM biased layers. In our sample

Glass/Gd40Fe60(100 nm)/Tb12Fe88(50 nm)/Al(4.5 nm)/Al2O3(3.5 nm)

grown by evaporation, both Gd40Fe60 and Tb12Fe88 are amorphous 

ferrimagnets in which the Fe and rare-earth magnetic moments are 

antiferromagnetically coupled. In Tb12Fe88, the iron contribution to the

magnetization is dominant, and the net magnetization of the alloy points

antiparallel to the terbium spins. Tb12Fe88 is a soft magnetic material

(i.e., it has a small coercive field) at room temperature but becomes hard

upon cooling. In Gd40Fe60, the contribution from the Gd is dominant,

and the net magnetization is parallel to the Gd spins. GdFe is a soft 

magnetic material at all temperatures.

Analogous to classic exchange-spring magnets [4], the competition

among the anisotropies, interlayer exchange coupling and Zeeman energies in our GdFe/TbFe bilayer gives rise to a rich magnetic phase diagram

in which spin-twists form near the interface. PN

imaging vertical domain walls in ferromagnetic 

layers [4], as it provides a depth profile of both 

the vector magnetization. PNR measurements w

NG-1 reflectometer with the neutron polarizatio

applied field maintained parallel to the TbFe un

tion in the sample plane. Polarization efficiencie

dependent magnetic and structural properties w

PNR data with a model for the scattering length 

possibility for a smooth magnetic twist in either 

[4]. While the fits were quite sensitive to the ma

TbFe layer as well as the GdFe magnetization cl

interface, they were much less sensitive to GdFe 

glass substrate due to the large Gd absorption.

FIGURE 1: a) Magnetization as a function of field f

at 300 K. b) Depth profile of the angle between the 

the positive field direction (0o) obtained from fits t

30

-400 -200 0 

-1.0

-0.5

0.0

0.5

1.0

0 20 40 60 80 100 

0

40

80

120

160

200

Magnetization (Relative Units)

Field (1000 Am /4π)

TbFe Gd

 7000

 500 

 200

 30

 Depth (nm)

 Angle Relative to Field (degrees)

-1
1.59×10

A/m in order to flip only the soft GdFe, and not the TbFe. HE

of the resultant hysteresis loops exhibits a pronounced dependence upon

the cooling field, Hcf. For example, HE increases from -6.4×103 A/m to

7.9×103 A/m with Hcf, and HE crosses zero at Hcf = 4.0×104 A/m [3].

FIGURE 2: PNR spectra obtained in a field of 1.59×104 A/m after cooling the

GdFe/TbFe sample from 300 K to 15 K in a 5.6×105 A/m field.

To best exemplify the relationship between the exchange field HE, the cooling

field Hcf, and the frozen TbFe spin configuration, we contrast here PNR

results obtained after cooling in fields of 5.6×105 A/m and 1.59×104 A/m,

which give rise to negative and positive bias fields (HE = 4.0×103 A/m and 

-6.4×103 A/m) respectively. Figure 2 shows the PNR spectra and fit measured

in 1.59×104 A/m after field cooling in 5.6×105 A/m. The fit indicates that a

shallow IDW, with approximate thickness of 15 nm, is present in the TbFe

layer (Fig. 3a). We note that the magnetic structure of the TbFe layer is frozen

and nearly matches the one determined at 300 K (shown in Fig. 1b), as

expected [3]. The TbFe interface moment is not parallel to its anisotropy axis,

but is oriented at an energetically unfavorable angle of 110° relative to the positive field direction and thus gives rise to a positive biasing field. Upon reversing the GdFe magnetization in a field of –1.59×104 A/m, the small IDW in

the TbFe layer vanishes and the TbFe interface moment realigns parallel to its

anisotropy axis (Fig. 3a). The TbFe and GdFe moments are antiparallel at the

interface (and throughout the entire layer) with the TbFe moments along the

field at 0o and the GdFe moments opposite the field at 180o.

In contrast, fits to the PNR data obtained after cooling in 

Hcf = 1.59×104 A/m reveal that a larger IDW approximately 30 nm 

thick (Fig. 3b) is frozen inside the TbFe layer and the 

moment is aligned antiparallel to the applied field at 

TbFe configuration favors full alignment of the GdFe 

the positive field direction at 0o, a domain wall is for

layer when the field is reversed below HE = -6.4×103 

structure in the reverse field involves two IDW’s (Fig. 3b

GdFe and TbFe moments are oriented completely oppos

in the Hcf = 5.6×105 A/m state (Fig. 3a). 

Overall, the PNR measurements of TbFe/GdFe bilaye

interface domain wall, mainly located in the TbFe lay

field cooling. PNR results also reveal that the orientat

magnetization at the interface, as well as the thicknes

is directly correlated with the magnitude and sign of 

bulk techniques. We further note that the cooling-fie

TbFe interfacial angle obtained from PNR fits approx

theoretical predictions [5]. PNR thus provides direct ac

spin configuration in this biased layer and our observat

structure in the TbFe “pinning” layer have clear implica

of the frozen AFM spin state in typical AFM/FM exchan

REFERENCES

[1] J. Nogues, I. K. Schuller. J. of Magn. Magn. Mater

[2] J. Nogues, C. Leighton and Ivan K. Schuller, Phys

1315 (2000). 

[3] S. Mangin, F. Montaigne and Y. Henry, Phys. Rev. 

140404 (2003). 

[4] K.V. O’Donovan, J.A. Borchers, C.F. Majkrzak, O. 

Fullerton, Phys. Rev. Lett. 88, 067201 (2002), an

[5] Y. Henry, S. Mangin, T. Hauet and F. Montaigne, t

published (2004).

0.00 0.02 0.04 0.06 0.08 0.10 0.12

Reflectivity

Q (Å -1 )

Non-spin Flip: + + - -

Spin Flip: - + + -

10 -6

10 -5

10 -4

10 -3

10 -2

10 -1

 1 R

R

R

R

GU3a) eptpoe ote age betweete a

the positive field obtained from fits to PNR data for diff

after cooling in 5.6×105 A/m. b) Depth profile of the ang

tion after cooling in 1.59×104 A/m. 
The low temperature behavior of quantum magnets can be

very different from that of their classical counterparts. While

classical magnets usually enter an ordered state at low 

temperatures with a particular pattern to their magnetic

structure, quantum magnets can tie up all their magnetic

moments into quantum mechanical entities (singlets) and

enter a non-magnetic state at low temperatures. We have

used the very high energy resolution afforded by the Disk

Chopper Spectrometer (DCS) at the NCNR to study the 

triplet excitations of one such quantum antiferromagnet,

SrCu2(BO3)2 by which we gain a microscopic understanding 

of how the quantium spins interact, and how this unusual nonmagnetic state dissolves away as the temperature is raised.

Layered quantum magnets have been at the forefront of condensed matter physics research in large part due to their relevance to high temperature superconductivity. Two-dimensional copper-oxides, in which conducting holes are introduced, provide the framework for much exotic

behavior, with high temperature superconductivity being the best appreciated example. More broadly, quantum antiferromagnets are of interest

because the paradigm for their behavior is not the orderly, antiparallel

arrangement of magnetic moments in a Neel state, but the formation of

singlets in which the magnetic moments lose their spin-up or spin-down

identity and reside in a quantum mechanical superposition of both spinup and spin-down.

SrCu2(BO3)2 is such a quasi-two dimensional quantum antiferromagnet.

Quantum spin 1/

2 magnetic moments reside on the Cu2+ sites in the

tetragonal structure shown in Fig. 1. There the tetragonal basal plane is

shown and it can be seen that the Cu sites are arranged in orthogonal

dimers, pairs of Cu2+ sites, which decorate the two-dimensional square

lattice. The leading terms which describe how the spin 1/

2 magnetic

moments interact are given by an intra-dimer an

interaction, J, as well as an inter-dimer exchang

also known to be antiferromagnetic. This is also i

FIGURE 1: A schematic drawing of the basal plane 

is shown (left) which highlights the Cu2+ dimers (r

bar). The leading order exchange interactions are il

diagram which shows the nearest-neighbor (nn) intra

neighbor (nnn) inter-dimer (J’) antiferromagnetic inte

Hamiltonian for this system is given in the lower righ

A remarkable feature of this model for interactin

it was considered theoretically and solved exact

Sutherland [1]. It is known, for example, that i

relative to J’, the low temperature state of such a 

magnetic collective singlet, in which all the spin 

are tied up in singlets within the dimers. In con

approximately 0.69, then a somewhat complica

state is formed at low temperatures. Early chara

SrCu2(BO3)2 on the singlet ground state side of th

scattering measurements [3] by Kageyama and co

singlet-triplet spin excitations as well as multi-trip

32

 Nea

Neighb

 (n

B

H = J ∑ S

nn 
Inelastic neutron scattering measurements were carried out on a large single crystal of SrCu2(11BO3)2 using both the spin-polarized triple-axis

spectrometer (SPINS) at the NCNR and DCS. Measurements on SPINS

established the two dimensional nature of the magnetic scattering. The

DCS measurements were performed with 5 Å incident neutrons, giving

an elastic energy resolution of ≈ 0.09 meV, and this allowed us to examine fine detail in the dispersion of the triplet excitations. We carried out

these measurements in the (H,0, L) reciprocal lattice plane. The DCS

measurements could then integrate up the inelastic scattering in L, so as

to continuously map out the triplet dispersion along [H, 0] within the

basal plane. The resulting map at low temperatures is shown in the top

panel of Fig. 2. It can be seen that the three triplet excitations are clearly

resolved. Their dispersion can be understood in terms of sub-leading

contributions to the interactions between the quantum s = 1/2 magnetic

moments (i.e., considerations other than J and J’) which must be allowed

by the symmetry of the crystal structure. 

FIGURE 3: The normalized temperature dependences of 

near 3 meV measured on SPINS (blue) and DCS (black) 

state near 4.85 meV measured on SPINS (red). The inset 

malized SPINS data. This unusual temperature dependen

tracked by the complement of the dc-susceptibility, 1-χ, 

localized nature of the excitations.

REFERENCES:

[1] S. Shastry and B. Sutherland, Physica (Amsterdam

1069 (1981).

[2] S. Miyahara and K. Ueda, Phys. Rev. Lett., 82, 37

[3] H. Kageyama et al, Phys. Rev. Lett., 84, 5876 (20

et al., Phys. Rev. Lett., 87, 167205 (2001).

0.00

0.05

0.10

0.15

0.20

0.25

2.5 2.7 2.9 3.1 3.3 3.5

E (meV)

Intensity (arb. units)

H = -1.0

H = -1.5

H = -2.0

2.5 

[H,0,0]

-2.5 

2.0 1.5 

1.0 

0.5

[H,0,0]

FIGURE 2: High-resolution inelastic neutron scattering data from DCS is

shown in the top and bottom panels. The bottom panels are cuts through

the scattering map displayed in the top panel which approximate constantQ scans of the [H,0,0] form. The middle panel shows how subleading,

Dzyaloshinskii-Moriya (DM) interactions manifest themselves in such a

high-resolution experiment. Out-of-plane interactions are responsible for

the full bandwidth of the scattering, while in-plane DM interactions give rise

to the small energy gap at [1.5, 0, 0].

-0.25

0.0

0.25

0.5

0.75

1.0

1.25

0 5 10 15 

Temperature (K)

Intensity (arb. units)

3 meV

4.85 meV

DCS

1- χ

0

1000

2000

0 10 

Counts/ Mon

Temper
Lead-oxide relaxor ferroelectric compounds exhibit the highest

known piezoelectric coefficients and strains and are thus

exceptionally attractive for device applications. Nanoscale

regions of randomly oriented polarization, i.e., polar nanoregions or “PNR,” form within these compounds well above Tc,

and give rise to strong diffuse scattering. Cooling these 

relaxors in an external field from above Tc is believed to produce a microscopically uniform polar phase via rotation of the

PNR, much like the case when field-cooling a ferromagnet.

Surprisingly, the diffuse scattering in Pb(Zn1/3Nb2/3)O3

doped with x = 8 % substance fraction of PbTiO3, for which

the piezoelectric properties are greatest, persists upon field

cooling, and is even partially enhanced. Further, the memory

of the field reappears after heating the system above Tc, and

then cooling in zero field.

The relaxor ferroelectric compounds PbMn1/3Nb2/3O3 (PMN),

PbZn1/3Nb2/3O3 (PZN), and their solid solutions with PbTiO3 (PT) have

received enormous attention in the materials science and condensed matter physics communities due to their record-setting dielectric and piezoelectric properties [1]. They have supplanted lead zirconate (PZT) ceramics as the basis of state-of-the-art piezoelectric sensors and actuators,

which are used to convert between mechanical and electrical forms of

energy, and they show promise as nonvolatile memories. A distinguishing property of relaxors, as compared to classic ferroelectrics, is the

appearance of nanometer-sized regions of local, randomly oriented,

polarization at the so-called “Burns temperature” Td [2], which is several

hundred degrees above the ferroelectric transition temperature Tc. These

polar nanoregions (PNR) are believed to play a key role in the unusual

relaxor behavior [3]. Several models based on random fields in a dipole

glass [4] have been proposed to explain the properties of the PNR. As the

PNR represent small regions of polar order, they 

temperature dependent diffuse scattering that gr

decreasing temperature as seen with both x-ray 

methods, and that grows monotonically with de

addition, the PNR have been imaged directly wi

response force microscopy techniques.

Many unsolved questions concerning the PNR r

the ferroelectric phase transition, or do they imp

the PNR from merging into the surrounding, ma

ronment below the ferroelectric phase transition 

studies of ferroelectrics, an external field is often 

the system responds. Yet few studies to date hav

response in relaxors to an electric field. A previo

diffuse scattering in a PZN based compound res

when field cooled (FC) in an electric field [5]. T

measured transverse to the (300) Bragg peak is 

field applied along the [001] direction, whereas 

orthogonal (003) Bragg peak is significantly sup

anisotropic response suggests that those PNR ha

polarizations can be forced to “melt” into the su

ly polar environment with the assistance of an e

ducing a more “microscopically-uniform” polar 

One of the most studied relaxor systems is PZN

ovskite structure. When doped with PbTiO3, sin

are obtained that can exhibit even higher piezoe

single crystal examined in our study had the op

responses of x = 8 %. Because PZN-8%PT has a 

state with <111> type polarizations at low temp

investigate the effect of an electric field applied 

The neutron diffuse scattering was measured in 

plane near the (300) Bragg peak at 300 K < Tc ( 

data are shown in Fig. 1.

34
When the crystal is zero-field cooled (ZFC), the diffuse scattering geometry is symmetric about the [100] axis, and forms the butterfly-shape with

“wings” of equal intensity on each side shown in Fig. 1(a). This is consistent with the three-dimensional diffuse scattering distribution consisting

of <110> rod-type structures, where PNR with different polarizations

contribute to different <110> diffuse rods. Because of the non-zero outof-plane resolution in our measurements, when moving away from the

center of the Bragg peak in the (HKK) plane, tails from the <110> rods

are then picked up. This results in the butterfly-shaped pattern, which is

symmetric about (300), as required by the crystal symmetry. The application of a moderate electric field of E = 200 kV/m along the [111] direction while still at 300 K did not change the diffuse scattering, which suggests that the PNR are robust in the ferroelectric phase. The sample was

then heated to T = 500 K, and the 200 kV/m electric field along [111]

was applied again. This time, as shown in Fig. 1(b), the diffuse scattering

pattern becomes asymmetric with respect to the [100] direction. The left

“wing” is clearly enhanced, while the right one is suppressed.

A more detailed look at the temperature dependence of the diffuse scattering is shown in Fig. 2, where linear scans measured along (2.9,K,K)

(corresponding to the dashed line in Fig. 1) are plotted. In the ZFC

state, the symmetric double-peaked profiles indicate that intensities from

both wings increase evenly with cooling. In the FC state, the intensity of

the left wing starts to increase below Tc, while the right wing remains

almost the same. At 300 K, the left wing intensity is clearly much higher

than that it is in the ZFC state. Upon removal of the electric field at 

300 K, the asymmetric diffuse pattern persists, indicating that the PNR

are frozen into the FC configuration. This behavior is quite similar to

that of a spin glass system where cooling through Tc with and without an

applied magnetic field leads to different final states, and the difference is

only observable below Tc .

ally retained by the PNR after the field is removed. T

applied field reappears even after heating the system 

cooling in zero field.

FIGURE 2: Linear cuts through the diffuse scattering sho

formed at (2.9,K,K), after the sample was ZFC (top pane

panel), measured at temperatures of 300 K, 400 K, and 

lines are fits to a sum of two Gaussian peaks.

REFERENCES:

[1] S.-E. Park and T. R. Shrout, J. Appl. Phys. 82, 18

[2] G. Burns and F. H. Dacol, Phys. Rev. B 28, 2527 

[3] L. E. Cross, Ferroelectrics 76, 241 (1987).

[4] R. Pirc and R. Blinc, Phys. Rev. B 60, 13470 (199

Phys. Rev. B 67, 094110 (2003).

[5] P. M. Gehring, K. Ohwada, and G. Shirane, Phys. 

014110 (2004).

[6] Guangyong Xu, P. M. Gehring, and G. Shirane, su

Phys. Rev. Lett.

PZN - 8PT 300 K

(2.9,K,K) [r.l.u.]

Intensity [counts/min]

250

500

250

 0

 0

ZFC

E = 0

FC

E = 2 kV/cm 300 K

300 K

500 K

-0.2 -0.1 0 0.1 

500 K

400 K
Spins located in the plane of an equalateral triangle are geometrically frustrated if they are coupled antiferromagnetically.

As a compromise, they can order by rotating 120 ̊ with

respect to each other as you go clockwise around the 

triangle. They can rotate to the right or to the left, and these

arrangements have different handedness (chirality). In a 

conducting material having such a textured system of spins,

electron transport is affected, possibly displaying an anomalous Hall effect. By manipulating the spin texture one may 

be able to control the transport properties to possibly make

spintronic devices. 

Using new chemical synthesis methods, we have produced large single

crystal samples of iron jarosite, KFe3(OH)6(SO4)2, an ideal Kagomé lattice antiferromagnet. The Kagomé lattice antiferromagnet, formed of corner

sharing triangles, is one of the most highly frustrated two-dimensional (2D)

lattices. This material possesses robust chiral correlations related to the

arrangement of spins around triangular plaquettes. Combined thermodynamic and neutron scattering measurements reveal that the phase 

transition to the ordered ground-state is unusual [1]. At low temperatures, application of a magnetic field induces a transition between states

with non-trivially different spin-textures. 

The magnetic Fe3+ ions of jarosite have spin-5/2 and lie at the corners 

of the triangles of the Kagomé lattice, shown in Fig. 1. Since the interaction is antiferromagnetic, the spin system is frustrated, and the cornersharing arrangement leads to a higher degree of degeneracy for the

ground state compared to the triangular lattice. Even though the 

Kagomé lattice antiferromagnet should not order at any non-zero 

temperature, the compound KFe3(OH)6(SO4)2 orders magnetically 

in the “q = 0” arrangement (shown in Fig. 1a) below TN ≈ 65 K due to

small anisotropy terms in the spin Hamiltonian, where q is the modulation wavevector. The ordered spins can be decomposed into three 

sublattices, with the spins on each triangle label

The vector chirality for each triangle may be defi

For the 

this vector is parallel to the c-axis with amplitud

ordered state, each triangle has positive chirality 

spins point directly toward or away from the ce

An ordered phase on a Kagomé lattice is charac

parameters (the sublattice magnetization and th

that have different symmetries. An intriguing po

these symmetries are broken at different temper

FIGURE 1: The Kagomé lattice with spins arranged 

tions. a) The “q = 0” structure, which is the ground 

iron jarosite. The spin arrangement has uniform, p

cated by the + within each triangular plaquette. b) 

ment with staggered vector chirality, known as the 

The first hints of the interactions that drive the 

from magnetization measurements. With the fie

to the Kagomé plane, a sharp peak appears near 

transition to the 3D magnetically ordered state a

ferromagnetism along the c-direction. Recent th

antisymmetric exchange, via the Dzyaloshinskii-

may induce such a moment by canting the spin

This interaction causes the spins on each triangl

36

a b

b

c a

Kv = (S1 × S2 + S2 × S3 + S3 × S1). 2

3√3
plaquette as Ks = S1 • S2 × S3. The presence of this type of chirality (in

static or fluctuating forms) can have important consequences in strongly

correlated electron systems, such as yielding an anomalous Hall effect in

metallic materials. In iron jarosite, we have discovered a phase transition

in which a net scalar chirality can be “switched on” by a magnetic field. 

FIGURE 2: Measurements of the field-induced transition to a state with nonzero scalar chirality. a) Magnetic moment, m, versus applied field for several

temperatures with H || c. (Note that M ∝ m.) The HC values indicate the

fields where dM/dH has a maximum. b) HC versus temperature. The inset

depicts the change in the spin configuration below and above HC. The solid

line in b) correspond to power-law forms for HC and M with the exponent 

β = 0.25 and TN = 64.7 K.

In order to probe the microscopic behavior of the magnetism in the temperature regime above TN, we performed inelastic neutron scattering

measurements of the spin fluctuations at T = 70 K within the L = 0 plane

of reciprocal space. For the 3D ordered spin structure below TN, the

stacking arrangement of the planes doubles the magnetic unit cell with

respect to the structural unit cell such that the magnetic Bragg peaks

occur at half-odd-integer values of L (L ≠ 0). However, for temperatures

above TN, the correlations between layers are destroyed and the 2D spin

fluctuations yield “rods” of scattering in reciprocal space along the 

L direction. The scans in Fig. 3a pass through the 2D rods of scattering

and directly measure the dynamic structure factor of the spin correlations

of the single Kagomé planes in iron jarosite. 

A reciprocal space map of the intensity of the spin fluctuations is shown

in Fig. 3a. First, the fact that the intensities are centered within the 

structural Brillouin zones indicates that the fluctuations have the q = 0

arrangement. The absence of scattering at the (2,0,0) position is 

consistent with this spin arrangement. Secondly, the 

intensities at the (1,0,0) and (1,1,0) positions reveal 

tions have XY symmetry at this temperature (the spin

try within the Kagomé plane is not broken). In contr

tures in the 3D ordered state, a preferred spin directi

intensities at (1,0,L) and (1,1,L) differ considerably. 

short-range q = 0 correlations in the 2D fluctuations 

arrangement of the vector chirality. In each region of 

vector chirality must be uniform (all positive or all ne

quette). We calculated the neutron scattering intensit

q = 0 correlations between coplanar spins assuming o

ty. Our model calculations are based on 7-unit cell cl

we have averaged over all spin directions within the 

results are shown in Fig. 3b, and the agreement with 

The presence of vector chiral order above TN may be 

in light of the DM interaction. 

Our measurements of this ideal Kagomé material rev

behavior related to two types of spin chirality: vector 

interaction is a significant perturbation to the Heisen

and strongly influences the low temperature physics. 

tor spin chirality is ordered even in the absence of br

symmetry. In the ordered state below TN, we have di

induced transition to a state with non-zero scalar chi

als based on jarosites may be promising candidates fo

pling between non-trivial spin textures and the transp

frustrated systems. For example, carrier-doped comp

exhibit an anomalous Hall effect of topological origin

sibly have useful applications in spin-based electroni

REFERENCES:

[1] D. Grohol, K. Matan, J.H. Cho, S.-H. Lee, J.W. Ly

Y.S. Lee, Nature Materials 4 (4), 323 (2005).

H [10 A m /4π] c

H T [K] [10 A m /4π]

a b

0 2 0

50 K

4 6 8 10 12 14 16

65 K

60 K

2 55 K

3

4

5

6

1

Hc

Hc

Hc

 6

 4

 2

 0

 8

10

12

14

H||c

H < H H > H

H||c

c c

0 70 10 20 30 40 50 60

m [ T m kg ] 3 -2

7 -1

7 -1

plot on the right depicts √3 × √3 correlations. Both calcul

case in which there is no preferred spin direction within t
Giant magnetoresistance (GMR) has greatly advanced our

understanding of exchange coupling and spin-dependent scattering and has revolutionized magnetic recording. In the conventional view, GMR requires the fabrication of artificial magnetic heterostructures, i.e., chemical interfaces are required.

Using small-angle neutron scattering (SANS), we show here

that a certain perovskite oxide (La1-xSrxCoO3) can phase separate into ferromagnetic metallic clusters in a non-ferromagnetic matrix, and that this leads to a GMR effect. We argue

that this system is a naturally forming analog to the artificial

structures fabricated by depositing nanoscale magnetic particles in a metallic or insulating matrix, i.e., this material displays

a GMR effect without the introduction of chemical interfaces.

The colossal magnetoresistance (CMR) in bulk perovskite oxides, and the

GMR in artificial metallic heterostructures seemingly originate from very

different physics. Recent progress in magnetic phase separation however,

has shown that heterogeneity also plays a key role in understanding

CMR, as these randomly doped oxides can exhibit spatial coexistence of

ferromagnetic (F) metallic and non-F insulating regions. Doped cobaltites

such as La1-xSrxCoO3 (LSCO) have been shown to exhibit this phase

inhomogeneity where at low x the non-F regions dominate and the system behaves as a semiconducting spin-glass, whereas at high x (x > 0.18)

a metallic F is found. In this work SANS was employed as a probe of this

magnetic inhomogeneity. The wavevector transfer (q) dependence of the

SANS from LSCO is shown in Fig. 1 for x = 0.3 (i.e., in the F metallic

phase) where the Curie temperature, TC = 220 K. Strong magnetic scattering is observed, following the Porod form, I(q) ∝ q-4, due to scattering from

a 3-D distribution of “hard spheres” of radius R in the regime q >> R-1.

This is often observed in Fs due to scattering from domains and observation of this form down to q = 0.01 Å-1 implies that this x = 0.3 sample

exhibits long-range F order. For T > TC, I(q) consists of weak scattering

from the chemical microstructure, while near TC 

observed at high q. This follows the Lorentzian fo

with I

0 and κ constants, due to the quasielastic cr

FIGURE 1: q dependence of the absolute SANS int

Note that I(q) ∝ dΣ/dΩ

Examining Fig. 1 it is clear that the scattering ca

q part (from long-range F order) and a higher q 

short-range fluctuations). We therefore present t

plotting the low q intensity (Fig. 2, top panel) a

(middle panel), along with the T dependence of 

(bottom panel). Starting at x = 0.30, which has 

find a sharp increase in the low q intensity at TC

M(T). The high q data show a narrow peak near 

critical scattering. At x = 0.18, the critical comp

order, the low q scattering is less intense and ha

whereas the high q scattering exhibits a wide pe

long-range F order is barely stable. At x = 0.15 th

with no transition to long-range F order. In this 

shows a T dependence that closely mimics M(T)

and x = 0.30. Given that this high q intensity is 

short length-scale F correlations it is clear that t

at x = 0.15 results from F clusters. 

38

0.01 0.1

10-3

10-2

10-1

100

101

102

103

Lorentzian

 q-4

(Porod)

q [Å-1]

x = 0.30 12 K (< 

225 K (

282 K (

dΣ /d

Ω [cm-1]
The Lorentzian form allows for the extraction of the magnetic correlation

length, ξ, as shown in Fig. 3. At x = 0.30 the spin correlations form

above TC and ξ diverges at TC due to the onset of long-range order. For 

x = 0.18, however, the correlation length, does not diverge, although it

increases near TC. For the case of x = 0.15 no critical divergence exists

due to the absence of a transition to long-range order. Instead, ξ increases

below 150 K (Fig 3(c)), due to nucleation of isolated F clusters, with 

ξ ≈ 20 Å at low T. 

FIGURE 3: T dependence 

of the correlation length 

for x = 0.30 (a), 0.18 (b)

and 0.15 (c). The bottom

panel also shows the 

T dependence of the 

magnetoresistance at 

H = 90/4π MAm-1 (90 kOe).

The picture that emerges at x = 0.15 is of isolated F clusters embedded in

a non-F matrix. In order to correlate the information provided by SANS

with the electronic properties, we examined magnetotransport in singlecrystals. The 10 K magnetoresistance (MR) for x = 0.15 is shown in 

Fig. 4. The observed large negative, which persists to high field, is hysteretic (with peaks in ρ at the coercive field, HC = 6.5/4π MAm-1), and

exhibits distinct differences between the virgin curve and subsequent

cycles. This effect only occurs at low T, as shown in Fig. 3(c), which

plots the T dependence of the MR at H = 90/4π MAm-1. The MR turns

on at the same temperature as the first indications of cluster nucleation,

meaning that the MR observed here only occurs when F clusters form in

the semiconducting non-F matrix. 

These MR phenomena exhibit remarkable similarity t

MR previously observed in artificial structures compo

particles in an insulating or metallic matrix (e.g. Co-S

composites display sizeable negative MR, noticeable d

the virgin curve and subsequent cycles, strong hyster

ρ at HC), as well as an MR that decreases rapidly beyo

limit. Quite simply, we suggest that LSCO is a natura

of these artificial granular systems. In our case the sy

phase separates into metallic F clusters embedded in 

matrix of hole-poor non-F material. The hysteretic low-

spin-dependent transport between F clusters. ρ is maxim

M = 0 and the cluster magnetization vectors are random

reduced in applied fields due to alignment of the cluster 

These qualitative statements can be strengthened by qua

Specifically, in the artificial matrix systems MR ∝ (M(H)/M

saturation magnetization. The agreement with this scalin

Fig. 4, where the solid line depicts the measured (M/MS)

shown that in the insulating matrix systems, ρ = ρ0exp(T

T0 constants, due to hopping between clusters in the pre

energy penalty. Such a T dependence is indeed observed 

In summary, we have shown that the spontaneously p

ovskite oxide La1-xSrxCoO3 is the first known natura

GMR structures composed of ferromagnetic particles 

ferromagnetic insulating or metallic matrices. We obs

lar GMR effect even without the deliberate introducti

faces. Our work demonstrates the feasibility of fabric

homogeneous solids where magnetic phase separatio

tion of magnetoelectronic heterostructures with usefu

REFERENCES

See J. Wu et al., Phys. Rev. Lett. 94 037201 (2005) and 

0 50 100 150 200 250 300

0

12

24 (c)

T [K]

0

30

60 (b)

Tc 0

30

60

90 (a)

Tc

0

30

60

90

-∆ / 0 -∆ / [%]

0

[Å]

x= 0.30

x= 0.18

x= 0.15
Ferroelectricity is the spontaneous electric polarization of a material, and is an electric analogue to magnetic ordering such as ferromagnetism. Although there are many ferroelectric and magnetic materials, very few have simultaneous magnetic and ferroelectric order. Among this rare class of solids, known as mutiferroics,

only a select few exhibit significant coupling between the magnetic

and ferroelectric properties. The origin of this unusual coupling is

not yet well understood, and these exotic materials have attracted added attention recently because of the intriguing possibility 

of using these coupled order parameters in novel spintronic device

applications. We have performed magnetic neutron scattering

studies at the NCNR’s BT-2 triple-axis spectrometer of two multiferroics that exhibit significant magnetic-ferroelectric coupling,

hexagonal HoMnO3 [1] and perovskite TbMnO3 [2]. Our results

are crucial first steps towards a fuller understanding of the interaction between magnetism and ferroelectricity in multiferroics.

FIGURE 1: Neutron scattering measurements (left) are used to determine the

magnetic structure of HoMnO3 (middle) and the transitions between these structures. Top and side views of the crystal structure are shown on the right. The

middle panel shows projections of the moments of the bottom layer, z = 0, and

middle layer, z = 1, Mn3+ ions are located at the center of the orange bipyramids.

In hexagonal HoMnO3, magnetic Mn3+ ions (su

form two-dimensional (2D) triangular lattices of 

the a-b plane, which are then stacked in an alter

c axis (see Fig. 1). Below around 875 K, these sh

the Ho3+ ions between these sheets in the c dire

the ferroelectric order. Neighboring Mn3+ spins 

antiferromagnetically coupled, and below 72 K 

ed system orders in a structure where adjacent s

angle. At around 40 K, HoMnO3 undergoes a s

tion with a sharp dielectric anomaly, indicating 

between the ferroelectric and antiferromagnetic 

FIGURE 2: Phase diagram of HoMnO3 as a function 

magnetic field.

We have established the magnetic phase diagram 

temperature and magnetic field using single-cry

The magnetic ordering temperature of HoMnO3 

up to 7 Tesla, but a magnetic field does strongly 

tion transitions that occur within the ordered ph

At very low temperatures, the magnetic phase d

40

0 20 40 60 80 0

2000

4000

6000

8000

10000

12000

Temperature (K)

Integrated Intensity (arb. units)

(1,0,0)

(1,0,1) High

Temperature

Intermediate

Temperature

Low

Temperature

Magnetic Neutron Scattering Magnetic Structures Crystal Structures

Ho

MnO5

bipyramids

Ho

Mn3+ magnetic

moments z = 0 z = 1

Low Temp

Intermediate

Temperature

High

Temperature

0

5

10

15

20

25

30

35

40

45

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Temperature [K]

B [Tesla]

H

C

I

L

F

F

H

Zero-

Magn

1

2

3

4

5

6

7

1

2

3

4

5 6

7
To elucidate the energetics of this material, we have also performed neutron scattering measurements of the spin-wave spectrum of HoMnO3.

Spin waves have different frequencies depending on their wavelength,

and by measuring the dispersion we can determine the strength of the

microscopic interaction between each spin on the lattice and its neighbors. Our results for the in-plane dispersion are shown in Fig. 3. The 

dispersion is independent of the out-of-plane direction, indicating that

the dynamics are almost completely two-dimensional.

We fit our results to a simple model with only two parameters: a nearestneighbor antiferromagnetic exchange J plus an additional anisotropy D

which makes spins prefer to lie in the a-b plane. The solid lines in Fig. 3

show our fit results, with J = 2.44 meV and D = 0.38 meV. Weaker interactions must be present in the system as well in order to explain the

complex magnetic behavior, but the quantitative results we extract for 

J and D are a critical first step towards being able to model the complex

interactions between the magnetism and the ferroelectricity in HoMnO3.

The complexity of the phase diagram revealed by neutron scattering indicates that there is still much to be learned about the complex physical

behavior of HoMnO3.

FIGURE 4: Crystal structure of

TbMnO3. Mn3+ ions are shown by

red spheres, Tb3+ by blue spheres,

and O2- by yellow spheres.

Unlike HoMnO3, the unit cell of TbMnO3 is based on a simple cubic,

rather than hexagonal, structure. The actual structure is more complicated, however, because lattice distortions break the cubic symmetry, as

shown in Fig. 4. TbMnO3 orders magnetically at 41 K in an incommensurate structure, meaning that the periodicity of the magnetic order does

not match the periodicity of the crystal structure. Below 28 K, TbMnO3

becomes ferroelectric. The application of a magnetic field of only a few

Tesla can switch the direction of electric polarization in the ferroelectric

state, indicating a strong coupling between the ferroelectric order and the

magnetism in this material. The mechanism for this coupling is not

understood, but may arise from the competing spin interactions. To

In order to determine this structure completely, we m

ing intensity at a large number of Bragg reflections ab

ferroelectric transition temperature. Our experimenta

compared to possible magnetic structures to find the 

fit the data. Above the ferroelectric ordering tempera

a longitudinally-modulated incommensurate structur

ferroelectric ordering temperature, however, the mag

a spiral structure that breaks the inversion symmetry 

This symmetry breaking by the magnetic order appea

for the emergence of ferroelectric order in TbMnO3.

Neutron scattering has proven to be a critical tool in 

ic properties of multiferroic materials. Our results fo

ture and dynamics of HoMnO3 and TbMnO3 have pr

insights into these systems and will help pave the wa

understanding of the interactions between magnetic a

order. The ability to tune magnetic properties with el

electric properties with magnetic fields has great tech

but we must first understand the underlying physics 

order to master their use.

REFERENCES

[1] O. P. Vajk, M. Kenzelmann, J. W. Lynn, S. B. Kim 

Phys. Rev. Lett. 94, 087601 (2005).

[2] M. Kenzelmann, A.B. Harris, S. Jonas, C. Broholm

Kim, C. L. Zhang, S.-W. Cheong, O. P. Vajk and J

in Phys. Rev. Lett. 

k (r.l.u)

Intensity 

0.0 0.1 0.2 0.4 0.3 

101

102

103

Q = (0,k,1)

T = 43 K

T = 36 K

T = 28 K

FIGURE 5: Neutron scattering measurements along the (0

TbMnO3 at different temperatures. Scans below 36 K are 

clarity. Arrows noted with q indicate scattering associated 

surate Mn3+ order, and arrows noted with t indicate scat

incommensurate Tb3+ order.
The study of single grain deformation represents a great

opportunity for improving many aspects of materials deformation models that describe aggregate behavior. In principle,

grains as constituents of polycrystals are single crystals, for

which there is a large body of data available. However, other

grains surround any given grain. Together, these grains

impose highly complex boundary conditions on each other 

that cannot be reproduced in a single crystal deformation

test. An example is an effect related to grain deformation

called “tenting” (Fig. 1, lower image) in which the deformation

of sub-surface grains causes protrusions or pits to form in

the grains directly at the surface. 

Due to the considerable difficulties in examining the 3D distribution 

of strains within a single grain, experimental data are scarce and, if 

available, were obtained by micro-beam [1] and surface scanning techniques [2]. The two principal methods that can provide non-destructive

measurements of properties such as strain, grain shape and orientation

on a single grain in situ, within a three-dimensional (3D) aggregate are

neutron diffraction and synchrotron x-ray diffraction. To our knowledge, 

the mapping of strains within a grain by neutron diffraction has not yet

been attempted. This is due to the requirement that beams approximately

one order of magnitude smaller than the grain size in typical alloys 

(< 100 mm) are required for 3D mapping. The resulting reduction in

intensity from the small beam size is accompanied by attenuation due to

path lengths of > 1 mm within the material and by tight requirements on

the positioning accuracy of the grain. 

A different approach was chosen here in which these problems are circumvented by increased grain size. Using an alloy of high purity aluminum with 0.8 % magnesium grain sizes of up to 10 mm were achieved

through a heat treatment. The grain used in the measurement is shown in

Fig. 1. The size of the gage volume was 1×1×1 mm3. Using a high-resolution mode of the BT-8 neutron diffractometer 

reflection at 2θ ≈ 90.4° was studied. As the typi

maximum (FWHM) in the undeformed state is 

contribution to the broadening after deformatio

sample was strained in a uniaxial tensile test in 

of 12.5 %. After each straining step, the sample 

cle goniometer for grain orientation (centering i

scattering plane), and then scanned in the X,Y a

sample table in 1 mm increments. The scan con

integrated intensity over a range of rocking angl

scattering plane), thus allowing the spatial mapp

rocking curve broadening. 

Classic peak broadening analysis considers aver

of grains. Peak broadening is split into two cont

from domain size and broadening from dislocat

strains. The deconvolution of the two effects req

a large range 2θ. The spatial mapping of a singl

hand, allows the unambiguous separation of str

rotation broadening. As a grain is subjected to n

stresses during deformation, different regions of 

grain are subjected to different levels of deforma

dislocation densities) as well as to rotations. The 

fragmentation of the grain that can be measured 

42

FIGURE 1: Tensile sample with the grain selected fo

the beginning and at the end of the experiment. Th

of 1 mm. The stereographic projection on the right 

direction close to the tensile axis.
rocking curves. The increase in grain fragmentation after each straining is

shown in Fig. 3. Grain fragmentation is the absolute difference |ω– – ωi

|

between the centroids of the individual rocking curves ωi and the grain

average ω–. The spatial distribution of the fragmentation indicates clustering of neighboring data points with similar values of fragmentation.

Regions in the grain with different dislocation densities yield broadened

rocking curves. The spatial distribution of the FWHM of each curve is

shown in Fig. 3. The grain average, i.e., the sum of all individual rocking

curves, contains both broadening through mutually displaced rocking

curves as well as the broadening of each curve itself (Fig. 4). The integral

broadening for the entire grain is therefore always larger than the average

FWHM and the average rotation (Fig. 5). As shown in Fig. 5, the contribution from rotations is always larger than that from the FWHMs and it

seemingly dictates the slope of the grain average curve. This is evident

from Fig. 4 that shows that the integral curve is very asymmetric due to

large rotations within the grain. This indicates the strong presence of slip,

which was also confirmed by the appearance of slip lines on the surface.

In the extreme case of complete slip dominance as the sole mode of

The experiment conducted here shows the feasibility 

ning in a single grain. The sum of all individual rock

integral curve of the grain whose broadening was stu

els of deformation. Between the two aspects of broad

and strain broadening – the contribution from rotatio

integral broadening.

REFERENCES

[1] N. Tamura, J.-S. Chung, G. E. Ice, B. C. Larson, J

Tischler, M. Yoon, in: “Proceedings Materials Relia

Microelectronics IX”, A.H. Verbruggen, et al., eds., 

Warrendale PA, 1999.

[2] D. Raabe, M. Sachtleber, Z. Zhao, F. Roters, S. Zaf

49, 3433 (2001).

FIGURE 3: Spatial distribution of the FWHM (dots) of each rocking curve.

The scale is identical to the scale employed in Fig.2.

0

200

400

42 43 44 45 46 

 [deg]

Inten

FIGURE 4: Selected individual rocking curves vs. the gr

vidual curves have both different positions and FWHMs

(222) reflection

0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0 2 4 6 8 10 12 

strain [%]

FWHM [deg]

grain, integral

average single

rotation

FIGURE 5: Separation of the broadening contributions fro

single FWHMs and the standard deviation of the individu

due to the measurement location being outside the grain. The size of the 

circles is proportional to the absolute value of the grain fragmentation. 

The different colors are for better contrast.
Gas pipelines have an enviable safety record in transporting

energy; this is due to detailed materials characterization and

stress analysis. In many types of integrity analysis (fracture,

fatigue, stress corrosion cracking, and weld cracking) the

residual stresses in the pipe must be included. These residual

stresses may arise from the forming operations involved in

producing the coil and pipe, seam welding the pipe, and girth

welding pipes together to form a gas pipeline. To perform

integrity analysis, and to assess methods of manufacture and

joining, it is necessary to measure these stresses. Neutron

residual stress measurements offer many advantages in

determining these stresses: the great penetrating power and

non-destructive nature of the measurement means that

stresses can be measured at a range of depths with good

spatial resolution. The evolution of residual stresses in pipeline

manufacture was investigated by neutron diffraction measurements at various stages in the manufacturing process: the strip

the pipes are formed from, the finished pipe, and the stresses

arising from welding these pipes together to make a pipeline.

Residual stresses are of special significance in gas pipelines as they are

designed with smaller safety factors than other major engineering components. For example, in engineering structures the factor of safety with

respect to the yield strength is typically 3 or more, with pipelines this is

1.25 (ASME B31.8). 

High gas throughput dictates high gas pressure, which makes the use of

high strength steels economical. The use of such materials in pipe manufacture invariably creates high levels of residual stresses that may contribute to premature failure by fatigue, stress corrosion cracking, fracture,

or lead to unacceptable deformation. 

In the manufacturing process, after a series of co

rolling operations, the resulting strip is wound o

from this to be fed into the pipe mill where the 

ing and longitudinal seam welding followed by 

expansion in the mill hydro-test (Fig. 1). Each o

es introduces cold work, thus increasing both th

through-thickness residual stresses. Failure mec

corrosion cracking, hydrogen assisted cold crack

affected strongly by residual stresses. Any study 

pipeline integrity must begin by assessing the re

built pipeline. Through-thickness stresses are pr

even shorter than the pipe diameter, thus allowi

measurements (Fig. 1). An additional source of 

which may produce high tensile stresses (up to 

by lower compressive residual stresses elsewher

post-weld heat treatment is not common in con

resulting stress state is essentially the initial resi

beginning of service of the pipe. Due to the lack 

residual stresses in shielded and manual metal a

pipelines there is considerable interest in non-d

of these stresses.

44

FIGURE 1: Left: Circumferential rupture in the hy

ment geometry for the corresponding hoop directio
The residual stress measurements were performed on the BT-8 instrument at the NIST Center for Neutron Research (NCNR). Measurements

were made without cutting the full ring of pipe so as to fully preserve the

stress field. A nominal gauge volume of 1 x 1 x 1 mm3 was used.

Unstressed d-spacings were measured on small coupons in the weld, heat

affected zone (HAZ), and in the parent material. 

Due to the severity of the coldwork at each stage of the manufacturing

process the stresses change substantially between stages (Fig. 2). The

depth dependence of the stresses is consistent with stresses introduced by

plastic bending (coil) and subsequent unbending (pipe). However, as the

coldwork (accumulated plastic strain) increases from coil to pipe bending

the maximum stresses found near the inner and outer surfaces increase as

well. The stresses in the unwelded pipe reach up to 60 % of the specified

minimum yield strength of ≈ 480 MPa. After girth welding even higher

stresses are found in the vicinity of the weld but not in the immediate weld

area itself (Fig. 3). Tensile stresses exceeding the minimum yield strength

are found at distances of about 2 × wall thickness on both sides of the weld.

An explanation for these high stresses in the parent metal is that as the

cooling, shrinking weld bead is restrained by the parent material adjacent

to it, the parent material goes into compression. At the same time the

parent material is also being heated which causes it to expand. The

expansion increases the compressive stresses on the adjacent parent

material as it is restrained by parent material further away from the weld.

The compressive stress exceeds the yield strength and the material yields

compressively. As the weld pool and adjacent material continue cooling,

the parent material adjacent to the weld is restrained from shrinking. The

magnitude of these tensile stresses is in accord with published data show

of the yield strength. As stresses in this direction hav

on flaws in the girth weld, the assumption that residu

yield stress magnitude would lead to an overly small 

size, thus sentencing many adequate welds to repair 

erably to construction time and costs. The acceptable 

girth weld is a function of the stress perpendicular to 

axial stress. It is customary to assume that the magni

stresses are equal to the yield strength, but in this cas

are approximately 2/3rds of the yield stress.

In summary, the results presented here provide a com

through-thickness residual stresses in gas pipeline at 

the manufacturing process. It was found that peak st

substantially with each manufacturing stage due to in

cold work. After welding the peak stresses are well ab

yield strength. This is important for reasons of pipeli

stress corrosion cracking, and for calibrating and veri

models of residual stress evolution.

REFERENCES

P. Michaleris “Incorporation of residual stresses into 

models” Edison Welding Institute (EWI) report 7412 

-400

-200

0

-3 -2 -1 012 34

Position (mm)

-400

-200

0

-3 -2 -1 12 34

Stress 

Unwelded pipe

FIGURE 2: Through-thickness stresses after coiling (left) and bending (right)

into pipe shape.

Inner wall

Outer wall

Weld centerline

Axial

Hoop

Radial

FIGURE 3: Stresses (MPa) after girth welding.
B = .

a* b*cos(γ*) c*cos(β*)

0 b*sin(γ*) –c*sin(β*)cos(α)

0 0 c*sin(β*)sin(α)

tedious work on a triple-axis instrument. Recent work has shown that a single

Laue measurement, requiring only minutes of neutron beam time, can be 

sufficient to derive the orientation matrix of a randomly oriented crystal 

of known or even unknown lattice parameters. The theory and user-friendly

computer programs have been developed that show how this may 

be accomplished. 

The geometry we use for analysis of Laue images is illustrated in Fig. 1. As

shown in this figure, the stereographic and gnomonic projections of reciprocal

vectors or diffracted beams are directly related to the locations of the diffracted

beams seen in a Laue pattern. Knowledge of the lattice geometry is not needed

to obtain these projections. Further, the projections may be observed from any

point of view, regardless of the actual crystal setting, which facilitates detection

of symmetry elements and offers the most convenient way of selecting three

non-coplanar reflections to be used to index the reciprocal lattice. Although

symmetry and cell dimensions are not directly derivable from Laue diffraction

patterns, our recent work shows that axial ratios and interaxial angles can be

derived from Laue images. 

In our algorithm, we assign Miller indices 100, 010 and 001 to the three vectors corresponding to the selected reflections. This fixes the directions of the

three reciprocal lattice directions and the angles between them, but not the

reciprocal unit cell lengths. Selection of a fourth vector, which is assigned

index 111, defines the relative magnitudes of the reciprocal unit cell,

a*/b*:1:c*/b*, and allows the Laue pattern to be indexed. It should be noted,

that the cell produced in this fashion may not reflect the full lattice symmetry,

and thus may not be the conventional unit cell, but the two cells will be 

closely related and previous work allows the lattice symmetry to be easily 

discovered. [1, 2] 

Recent work at HIFR has demonstrated the value of an orientation matrix for

triple-axis measurements [3]. The orientation matrix relates two Cartesian

coordinate systems: one system, labeled as OXRYRZR, which has the beam

running along YR, and XR pointing down, as shown in Fig. 1, is defined as the

instrument reference system. The second orthogonal system, labeled as

OXCYCZC, is defined relative to the designated reciprocal cell with ˆ

Xc = â*, ˆZc

= â*×ˆb*/|â*×ˆb*| , and ˆYc = ˆZc × ˆXc, where the caret indicates a unit vector.

NCNR work shows that the orientation matrix, U, of Busing and Levy [4] may

be derived directly from Laue images using the following procedure. We can

convert the coordinates of a reciprocal lattice point, hkl, expressed as column

vector h, to the system OXCYCZC (column vector xC) using equation xC = B

h, where 

We select two reciprocal vectors, h1 and h2 of k

reflections (e.g. h1k1l

1 and h2k2l2) and with kno

in the instrument reference system, XR1YR1ZR1, 

matrix B to determine the components of h1 an

Cartesian system. 

We then define a unit-vector triplet tc1 = h1; tc3 

tc2 = tc3 × tc1. From this triplet we calculate a n

matrix element Tcij is the X, Y or Z component (

ly) of tci in the crystal Cartesian system (OXCYC

pute matrix, TR, that relates the same set of uni

ment reference system (OXRYRZR) in a similar f

entation matrix, U, we note that it must relate t

so that TR = U Tc. Since Tc is orthogonal, we so

matrix as U = TR Tc

T. In practice, multiple rec

used in this procedure to reduce experimental e

REFERENCES

[1] A. Santoro, A. D. Mighell, Acta Cryst. A 26, 

[2] V. L. Himes, A. D. Mighell, Acta Cryst. A 43

[3] M. D. Lumsden, J. L. Robertson, M. Yethiraj

38, 405 (2005).

[4] W. R. Busing, H. A. Levy, Acta Cryst. 22, 45

ADV

46

Diffracted 

cted beam

 beam direction

Pri

Line of

 Reciprocal 

 lattice 

 vectors

Gnomonic

projectionplane 

Stereographic

projectionplane 

Project

Center of 

Reference 

 Ewald 

 sphere 

RG DS

Stere

pole

O

Crystal, ki

kf

XR

A possible Laue

Detector Plane 

g g

projection of th

vector onto the 

projection plan

OD = CR , giv

i.e., the gnomo

the line of reci

S G 

C

pole of

gnomonic

proj.

FIGURE 

how a r

from a 

the rela

stereog
length that are coated with neutron absorbing material. We have modeled

and tested a new type of neutron collimator made of 157Gd-doped

microchannel plates (MCPs) with only a few millimeters thickness, and yet

the rocking curve is sharper than conventional 0.5 ̊ collimators. The rocking

curve for existing MCP technology can be as sharp as 0.2 ̊ Full-Width-atHalf-Maximum (FWHM) and experiments with collimators only 0.6 mm

long confirm the accuracy of the numerical model.

Thermal neutron beams are usually collimated with a Söller slit collimator,

comprised of neutron-absorbing films supported on thin spacers, e.g., thin

single crystal silicon wafers or mylar films with absorbing coatings [1-3].

The shorter the collimator, the narrower the transmitting channel required

to achieve the same level of collimation. Recently, the stacking of 160 μm

thick silicon wafers coated with 4 μm of gadolinium metal achieved a 

2.75 cm long collimator with performance comparable to conventional 

collimators [2]. However, collimators can be substantially more compact if

the absorber-spacers are reduced to a thickness of few microns. The structural dimensions of commercially available microchannel plates (MCP) meet

these requirements with typical channel sizes of 6 μm to 15 μm and 2 μm

to 3 μm walls thicknesses. We have computer-modeled and tested available

MCPs (doped with 157Gd) as prototypical, very compact and highly efficient

thermal neutron collimators. 

Microchannel plates typically consist of millions of open channels fused

together into a monolithic structure, a section of which is shown in Fig. 1.

The channels are usually circular, hexagonal or square in cross-section, 6 μm

to 12.5 μm wide and spaced 7.5 μm to 15 μm center-to-center. The thickness

of the disk is typically 40 to 250 times larger than the channel diameter

(equivalent to 0.24 mm to 3.75 mm), and MCPs can be fabricated with a

cross sectional area as large as 10x10 cm2. Whenever the neutron trajectory

transects the microchannel wall, neutron absorption occurs from its reaction

with 157Gd (thermal neutron capture cross section ≈ 259 000 barns). 

Numerical modeling of the “ideal” rocking curve shown in Fig. 2a, 

indicates that MCPs with their tighter geometrical packaging are an attractive alternative to existing neutron collimator technology. Increasing the 

wall composition fraction of 157Gd2O3 from x = 0.003 to .03 substantially

improves the performance of collimators with aspect ra

though further increases of 157Gd concentration do no

collimation. The model does not include reflection and 

though the latter will give a moderate smoothing of the 

the ‘ideal’ rocking curve. 

The correctness of our model for the MCP neutron coll

confirmed by preliminary experimental measurements. 

plates tested (L/D =75:1, 8 μm circular channels with 1

doped with x = 0.03 of 157Gd) were systematically rota

the beam to map the neutron transmission. The result

Fig. 2b showing the collimation in two orthogonal plan

The predicted performance of the same MCP is only sli

measured maximum transmission (≈ 0.44) is equal to t

of the microchannel plates. MCP open areas of 60 % to 

The model indicates that transmission and collimation 

of a conventional 0.5 ̊ neutron Söller collimator is achie

rocking curves are possible using thicker MCP collimat

solid-core MCP collimators are feasible for significantly 

constructed using 25 mm thick pieces with channels w

6 μm, producing an L/D ratio of > 4000 [4]. The MCP

neutron optic layouts and better collimation than existi

REFERENCES

[1] Th. Krist and F. Mezei, Nucl. Instrum. Methods, 

[2] L. D. Cussen, et al., Nucl. Instrum. Methods, A47

[3] C. Petrillo, et al., Nucl. Instrum. Methods, A489 

[4] A. S. Tremsin et al., IEEE Trans. Nuc. Sci. 51(3) 1

FIGURE 1: a) Squarechannel and b) circularchannel MCPs doped

with 157Gd.

0

0.1

0.2

0.3

0.4

-2 -1 0 1 2

Intensity (fraction of main beam

φ = 80o

φ = 40o φ = 50o

φ = 0o

Rocking Angle [degrees]

a)

FIGURE 2: a) Modeled rocking curve for aspect ratio L/D 

up to 250:1 are readily available. b) Measured rocking c

0

0.1

0.2

0.3

0.4

-2 -1 

Intensity (fraction of main beam)

Rockin

)
Reference Materials® (SRMs) used for calibration and quality assurance purposes. Essentially no SRMs are certified for the small sample sizes typically

used [1] and direct utilization of most existing SRMs in solid sampling analysis

procedures is often difficult or even impossible either because trace components are not sufficiently homogeneously distributed in the sample, or their

homogeneous distribution has not been validated. To study the homogeneity

of SRMs at small sample sizes we have developed the established Instrumental

Neutron Activation Analysis (INAA) procedures of the NIST Nuclear Methods

Group [2] to accommodate the small samples with essentially no degradation

of uncertainty in the analytical results. These procedures have since become

an integral part of the development of a first material of a new generation of

highly homogeneous SRMs.

Based on models linking sample mass (m) to the homogeneity of particulate

materials, Kurfürst et al. [3] have proposed an elemental homogeneity factor

He that gives the relative standard deviation in percent for the element of interest if 1 mg samples were repeatedly analyzed and no analytical uncertainty

were to influence the result He = uHET √m [4]. Experimental determination of

uHET by INAA requires that small samples are prepared for INAA in the form

of pellets either by directly pelletizing 1 mg amounts of material in a 3 mm

diameter die, or preparing 70 mg to 100 mg amounts in a 13 mm diameter

die and then sub-sampling these pellets at 0.5 mg to 2 mg with a 1.5 mm

diameter corer. These small samples provide nearly ideal sample geometries

for high-precision assay by INAA. The procedural relative uncertainties are

generally 0.5 % to 0.7 % and very suitable for the intended purpose, with

counting statistics varying from 0.1 % to several percent depending on the

activity of the element. To minimize the counting uncertainty, these experiments mainly utilized a newly installed set of three high-resolution gamma-ray

spectrometers with ultra-high count rate capabilities. Count rates in short and

intermediate half-life assays reached up to 50 000 s-1. The spectrometers were

evaluated for high accuracy analysis of metals where expanded relative uncertainties of smaller than 0.3 % were achieved. The long counts were carried out

on a conventional detector system equipped with a sample changer. 

Investigations of homogeneity by INAA encompassed a number of different

materials before a sediment from the Patapsco River, Maryland, the SRM 2702

Inorganic Marine Sediment, was selected for development of the new generation SRM for solid sampling (small sample) analytical techniques. The new

material, SRM 2703, was produced with a smaller particle size distribution

than the original to assure homogeneity. For the acceptance of the material,

twelve test portions of SRM 2703 were analyzed by INAA, and the heterogeneity components were calculated by subtracting the analytical uncertainties

from the observed experimental uncertainty. The results for elements with 

ity for the observed elements at sample sizes of 1 m

observed elements ranged in their concentrations fr

(Al, Fe) to trace (Mn, Zn) and ultra-trace (Sc, V) co

origin, the material was accepted for certification. 

techniques subsequently confirmed homogeneity fo

elements such as Ni and Pb. 

TABLE 1. Homogeneity test results obtained by IN

SRM 2703. Reported are elements with low counti

Uncertainties are % relative values (1 s) for each co

Element Mass Observed Counting Other 

(mg) Uncertainty uncertainty uncertain

(estimate

Al 0.8 0.92 0.37 0.5 

As 0.7 2.22 0.84 0.7 

Ce 0.7 1.17 0.91 0.5 

Co @ 1723 keV 0.7 1.26 0.89 0.5 

Co @ 1332 keV 0.7 1.33 0.88 0.5 

Fe @ 1099 keV 0.7 1.26 0.77 0.5 

Fe @ 1292 keV 0.7 1.09 0.72 0.5 

La @ 487 keV 0.7 1.30 0.79 0.7 

La @ 1596 keV 0.7 1.39 0.78 0.7 

Mn @1811 keV 0.8 1.08 0.50 0.7 

Mn @2113 keV 0.8 1.04 0.66 0.7 

Na @1368 keV 0.8 1.21 0.87 0.7 

Na @2754 keV 0.8 0.80 0.79 0.7 

Sc @ 889 keV 0.7 1.00 0.99 0.5 

Sc @ 1121 keV 0.7 1.16 0.99 0.5 

Th 0.7 1.51 1.03 0.5 

V 0.8 1.49 0.90 0.5 

Zn 0.7 1.31 1.10 0.5 

* Factor could not be calculated because the observed experim

to the analytical uncertainty

The new generation SRM 2703 Sediment for So

sample) Analytical Techniques provides certified 

reference values for 7 elements, and information 

for a minimum sample size of 0.7 mg.

REFERENCES

[1] Survey of Reference Materials, International Ato

Vienna, Austria, IAEA-TECDOC-854 (1995), IA

[2] R. R. Greenberg, R. F. Fleming, and R. Zeis

10, 129 (1984).

[3] C.O. Ingamells, P. Swizer, Talanta 20, 547 (1

[4] U. Kurfürst, K.-H. Grobecker, M. Stoeppler, Tr

ADV

48
long term, it is clear that we must continue to expect continued high

demand for access to NCNR instruments. In response to these pressures,

this year the NCNR received a significant increase in funding to expand

access to the NCNR through the user program. Upgrading instruments

and then operating them in a robust user program will accomplish this

enhancement. During the past year the NCNR expanded access for the

reflectometer instruments and accelerated work on the new triple axis

spectrometers that will join the user program when completed.

We continue to make improvements to the many services that users

count on for accessing and using the NCNR. The process for coordinating user activities is very different from what it was just a few years ago.

Mass mailings and stacks of paper proposal forms have been replaced by

online proposal submission and review. A new User Office has been

established to aid users and visitors. In the coming year, our databases

will be completely revamped to integrate procedures such as site access

for users, safety training, instrument and equipment scheduling, and

publication of research results. 

The NCNR User’s Group (NUG) provides an independent forum for users

to give feedback on the operation of the NCNR. The NUG is organizing

its first election of officers and developing an online tool to collect feedback from the NCNR user community. The results from last year’s user

survey continue to influence how we allocate resources supporting data

analysis software, sample environment equipment, user access and health

physics training. 

scattering, probing length scales from 1 nm to about 

from about 30 neV to approximately 100 meV. Most 

receive ask for time on one of the CHRNS instrumen

30 m SANS diffractometer, a high-resolution USANS 

backscattering spectrometer (HFBS), the disk-choppe

(DCS), the neutron spin-echo spectrometer (NSE), an

triple-axis spectrometer (SPINS). CHRNS also plays a 

NCNR’s educational activities, through its annual wee

school on neutron scattering, for example, and its ou

ELEVENTH ANNUAL SUMMER SCHOOL

Every June, we host a summer school to introduce yo

mainly graduate students and postdoctoral researcher

practice of neutron scattering. Ever popular, the 2005 

applications for the 32 available slots. Sponsored by 

alternates in successive years between structural stud

reflectometry and dynamics studies using neutron sp

mat centers on hands-on instruction at the instrumen

performing actual experiments. Participants chose th

0

500

1000

1500

2000

2500

3000

3500

87 89 91 93 95 97 9

 year

NCNR Participants

 1st Cold Source Upgrade

In 2005 Research Participants were from:

 13 NIST Divisions and Offices

 36 U.S. Government Laboratories

131 U.S. Universities

 46 U.S. Corporations
g, g, ppp

were bracketed by a half day of lectures at the start of the school and by

two advanced-level invited talks on bio-membranes and complex magnetic oxides at the end. On the last day, the students learned how to

choose the best spectrometer for a particular experiment, and gave group

presentations to NCNR staff summarizing the experiments that they had

performed. The instructors’ commentary on the presentations and the

students’ evaluations of the instruction indicated that they departed

friends, with some good proposals and experiments foreseen in 

coming years.

COLD NEUTRONS FOR BIOLOGY AND TECHNOLOGY

The Cold Neutrons for Biology and Technology (CNBT) research initiative is a consortium dedicated to studies of biological membrane systems,

funded by the National Institutes of Health (NIH-NCRR), with contributions from NIST, the University of California at Irvine, the University of

Pennsylvania, and Johns Hopkins University. In addition to the abovementioned institutions, the CNBT partnership encompasses investigators

from Rice University, Carnegie Mellon, Duke, and the NIH-NIAAA, as

well as collaborators from the Los Alamos National Laboratory. The

CNBT collaboration includes the Advanced Neutron Diffractometer/

Reflectometer (AND/R) for structural biology, 10 % of the time on the

NG-7 30 m SANS diffractometer, a fully equipped biology laboratory, and

two state of the art computer clusters – one at NCNR and one at UC

Irvine – for molecular dynamics simulations. This combination provides

a powerful set of capabilities for US researchers interested in structural

biology problems that involve membrane systems.

regards its participation in the NCNR and collab

other members of the scientific community not 

investment for the company, but also as a good 

scientific health of the nation.

INDEPENDENT PROGRAMS

The Neutron Interactions and Dosimetry (NI

(Physics Laboratory) provides measurement se

fundamental research in support of NIST’s missi

technology and neutron physics. The NI&D gro

basic research with neutrons in the measuremen

parameters of the weak nuclear interactions, add

issues that are important in the understanding o

the cosmos. The neutron interferometry program 

most accurate measurements of neutron coheren

tests fundamental aspects of quantum mechanic

among world leaders in developing 3He based n

analysis techniques. The NI&D group, which op

high-resolution neutron imaging facility, has pio

of neutron phase imaging and the application o

fuel cell research. The NI&D group has initiated 

ed program to develop advanced neutron spectr

effective neutron interrogation and measuremen

for national defense and homeland security need

improves neutron cross-section standards throu

experimental work and maintains, and dissemin

dards for neutron dosimeters, neutron survey in

neutron sources.

50
archaeological contexts to specific production locations is currently 

being used to examine the manufacture and distribution of lead glazed

pottery in Mexico and the northern Spanish borderlands of California

and the American southwest. 

The Polymers Division of the Materials Science and Engineering

Laboratory works with the NCNR and industrial partners in several program areas including electronics materials, nanomanufacturing, selfassembling systems, polyelectrolyte solutions, and biomaterials. Several

neutron-based methods are employed in these studies including small

angle neutron scattering, neutron reflectometry, neutron diffraction, and

neutron spin echo spectroscopy. In the electronics materials program, the

NCNR provides unique measurements that impact next-generation photolithography, including the in-situ distribution of aqueous base and

water in ultrathin polymer films and the measurement of the spatial

extent of the deprotection reaction in model 193 nm and EUV photoresist materials. In the nanomanufacturing program, neutron techniques are

used to elucidate the underlying principles of dispersing and manipulating advanced materials such as carbon nanotubes and block copolymer

thin films. In the biomaterials program, NCNR instruments provide

important structure and dynamics information for tissue engineering,

regenerative medicine, and protein preservation.

ods, instrumental and radiochemical neutron activati

and RNAA). In aggregate, the techniques used by th

powerful set of complementary tools for addressing a

for both in-house and user programs, and are used to 

large number of NIST Standard Reference Materials.

The Center for Food Safety and Applied Nutrition

Drug Administration (FDA), directs and maintains a 

analysis (NAA) facility at the NCNR. This facility pro

analytical support for special investigations, and eme

complementing other analytical techniques used at F

tal, neutron-capture prompt-gamma, and radiochemi

radioisotope x-ray fluorescence spectrometry (RXRFS

gamma-ray detection. This combination of analytical 

diverse multi-element and radiological information to 

foods and related materials. The NAA facility suppor

assurance programs by developing in-house reference 

acterizing food-related certified reference materials w

agencies, and by verifying analyses for FDA’s Total Di

Studies include development of RXRFS methods for s

and food packaging materials for the presence of Pb, 

tially toxic elements, use of instrumental NAA to inve

residues in bread products, development of Compton 

niques for instrumental NAA, and use of prompt-gam

mine elemental compositions of NIST Ephedra Stand

Materials and commercial dietary supplements.
alignment, and replacement of the heavy water in the main and auxiliary

systems. The Reactor Operations and Engineering staff also performed 

a remote inspection of the reactor vessel interior, resulting 

in a detailed video record of the reactor vessel internals for benchmarking

and future reference. The condition of the reactor is excellent. The

extended shutdown was coordinated with the installation of the front end

of the new Multi-Analyzer Crystal Spectrometer (MACS) at NG-0.

Because of the close proximity of the MACS instrument to the NCNR

cold source, installation work in this area must be performed with the

reactor shutdown.

The NBSR is operating under a provision of the U.S. Nuclear Regulatory

Commission (NRC) that allows for continued operation after submittal 

of a timely application for license renewal. The original license for the

NBSR expired on May 16, 2004 and NIST submitted a timely renewal

application on April 9, 2004. NRC procedures are being followed in 

providing the schedule for the next steps in the NBSR license renewal

process. Work continues on reactor analysis and plant improvements in

preparation for these steps. Highlights from this year included replacement of reactor nuclear instrumentation and several console displays 

during the extended outage. We continue to study and analyze options

for a full replacement of the control panel with an improved, ergonomic

design. Other reactor license renewal goals were 

the secondary cooling water pumps and motors 

of the cooling tower replacement program. We 

ernization of the reactor building ventilation sys

replacing the RT2 in-core pneumatic sample ass

We have been very active in a variety of outreac

local government officials and with members of 

tions in an effort to share information about NIS

the ongoing license renewal process. On May 24

in a public meeting at the Gaithersburg Commu

NIST called “Getting to Know the National Insti

Technology: Neighbor, National Resource, and W

52

Operator Richard Beasley at the control console wit
laboratory equipment and supplies on the NCNRs website at

http://www.ncnr.nist.gov/userlab/.

One of the new laboratories is the result of a bioengineering research

partnership between the NCNR and five universities, with partial funding

from the National Institutes of Health. This Cold Neutrons for Biology

and Technology (CNBT) laboratory is equipped with a high volume laminar flow hood designed for working with acids (e.g., for cleaning substrates), a chromatography refrigerator; a large -40 oC freezer, a temperature controlled, 13 200 rpm microtube centrifuge, as well as standard wet

chemistry equipment for preparing biology-related samples for diffraction, reflectometry, and SANS experiments.

Another laboratory is dedicated primarily to sample characterization and

includes equipment for dynamic light scattering, infrared spectroscopy,

UV-Visible Spectrophotometry, gas chromatography, and an optical microscope with temperature controlled sample stage, camera and attachments

for fluorescence measurements. This laboratory also has a rotary evaporator for purifying solvents and a computer-controlled Langmuir-Blodgett

(LB) trough (see Fig. 1) for depositing multimolecular layer LB films on

solid substrates.

In addition to the above, there are laboratories with specialized equipment for x-ray diffraction, solid-state chemistry, surface and interface science, and general solution chemistry. Also implemented this year is a bar

The first measurements to characterize the performan

of-the-art thermal neutron triple-axis spectrometer at 

have been carried out and have met expectations. Th

features a choice of either a Cu(220) or a PG(002) do

monochromator, providing a continuous incident neu

from 5 meV to 500 meV. The 400 cm2 reflecting area 

mator yields as much as an order-of-magnitude gain 

sample compared with other thermal triple-axis spec

NCNR. The reactor beam and post monochromatic b

mators, slits, and filters) offer a wide range of choices 

olution and intensity of the instrument, with estimate

sample of approximately 108 n/cm2/s. 

The sample stage of the instrument includes two coa

one for sample rotation and one for the independent 

field coils, and a computer-controlled sample goniom

Polarized 3He cells are under construction for the ins

full polarization analysis with both monochromators 

dard analyzer crystals.

The BT-7 spectrometer is designed to be used with in

tomized analyzer/detection systems supported on air 

analyzer system will have a multistrip PG(002) analy

used in a horizontally focused mode, or in a flat conf

a linear position-sensitive detector or with convention

tors. All options will be under computer control and 

interchanged by the experimenter without requiring 

changes or user intervention. A separate diffraction d

in front of the analyzer for Bragg peak measurements

detectors embedded in the shielding behind the analy

ly monitor the neutron flux entering the analyzer sys

can also be used for measurements of the instantaneo

tion, for example, or with a radial collimator to deter

pattern over a limited angular range. This analyzer sy

advanced stage of development and is scheduled to b

2006. In the interim, a conventional analyzer system 

on air pads so that the instrument is now fully opera

FIGURE 1: Yamali Hernandez keeps a watchful eye on the Langmuir-Blodgett

trough in one of the NCNR’s recently renovated user laboratories.
FIGURE 2: Comparison of the beam intensities (monitor count rates) for 

the PG(002) monochromators for the new BT-7 triple-axis spectrometer and

the conventional triple-axis spectrometer at BT-2. The BT-7 monochromator

features vertical focusing that varies with energy, whereas the BT-2 monochomator has a fixed vertical focus optimized for 14.7 meV. The collimation

was open 50’ before and after the monochromator, respectively, on both

instruments. The much larger BT-7 monochromator provides more neutrons

that fully illuminate the sample over a wider range of incident energies. The

new double-focusing mode is seen to provide a dramatic gain in neutron

intensity by relaxing the wave vector resolution of the instrument.

INSTALLATION OF THE HIGH INTENSITY MULTI-AXIS 

COLD NEUTRON SPECTROMETER (MACS) BEGINS

While inelastic neutron scattering can, in principle, elucidate atomic scale

dynamics in almost any material, experiments on the most exciting new

materials are often impractical because high quality samples are too

small. Arguably, this is not a fundamental limitation of the technique but

one due to the lack of flux and detection efficiency of current instrumentation. The MACS project aims to increase both factors by an order of

magnitude in order to perform informative experiments on 1 mg samples

and to obtain comprehensive maps of inelastic scattering when larger

samples are available.

FIGURE 3: Designers Peter Hundertmark and Timothy Pike examine the 

drive mechanism that will rotate the sample and detector around the monochromatic beam transport system.

pg gp

all materials within 750 mm of the sample position 

FIGURE 4: Stephen Smee (left) and Gregg Scharffst

chromating system. Not shown are Joe Orndorff an

complete the team from the Instrument Developme

Hopkins University that designed and assembled th

Apart from the intense NCNR cold neutron sou

flux on sample is the monochromating system, 

from 1400 cm2 to 8 cm2. It consists of a variabl

mize background and to control wave vector res

radial collimation system to control energy resol

doubly focusing graphite monochromator. Thes

filled cask to reduce air scattering and pack shie

complex beamline elements. Figure 4 shows the

by the Instrument Development Group at Johns 

where they were designed and assembled. The m

system now stands ready for neutrons at the NC

All the equipment described above was installed 

late summer and early fall of 2005. Sample stag

installation will start in the fall so MACS can be 

experiments and friendly users in the spring of 

eventually become a CHRNS user facility for a b

54
has been designed to help the user get the most from his/her neutron

data. The project manager concept promises to greatly simplify the 

user experience because it allows a user to save a complete session 

(plots, reduction steps, data operations, etc.) and restore it at a later time.

Moreover there is much greater flexibility in DAVE II with the implementation of a document/view architecture. Multiple datasets can be loaded

simultaneously and multiple views (even of the same dataset) can be created (line, contour, image, surface and volume renderings using OpenGL,

the industry standard for high performance graphics). The visualizations

are feature-rich allowing simple creation of sophisticated plots resulting

in publication-quality output. Undo/redo functionality is implemented

allowing scientists to perform “what-if” types of analyses with ease, thus

enhancing the user experience. In the initial release, support for ASCII

and the current DAVE format are provided. Operations to perform 

specific data analysis tasks are being implemented and the initial data

reduction functionality is identical to that of the current version of DAVE.

DEPLOYMENT OF ELECTRONICS FOR LARG

DETECTOR ARRAYS

As the number of detectors on an instrument increas

themselves are buried in locations that are not readily 

of tuning the discriminator thresholds and periodical

banks for quality control becomes a major undertakin

Amplifier-Discriminator 2 (PAD2) system (Fig. 6), de

NCNR’s data acquisition and instrument control team

solution to the needs of instruments with a large num

This system consists of compact front-end modules c

tions of preamplifier, amplifier, and discriminator, co

that multiplex control and data signals for eight front

system controller that can set the gain and signal thre

tion of up to 2048 individual detectors. The different

employed allow for longer cable runs and greatly imp

tion over the existing TTL solutions. Live quality con

thanks to in situ pulse height analysis. A single point 

possible to tune the discriminator settings for detecto

or in vacuo. Taken in combination, the capabilities of 

groundbreaking and surpass anything available comm

was successfully deployed on the 32-detector BT-1 po

and the HFBS backscattering spectrometer in 2005.

FIGURE 7: Preamplifier-Amplifier-Discriminator 2 (PAD2

FIGURE 5:

Data in DAVE II can be 

imported, manipulated

and displayed in easily 

customizable yet 

sophisticated plots.
development of neutron reflectivity and

for his pioneering work in the exploration of many issues in interface science 

using this technique. 

Of particular note is how Dr. Majkrzak designed, optimized, and made

creative use of supermirror polarizers, integrating them into neutron

instruments that attain very low backgrounds and consequently the highest signal-to-noise ratios achieved anywhere. Moreover, Dr. Majkrzak and

his collaborators developed an exact, first-principles method to analyze

specular reflectivity data. The culmination of their efforts was a solution

to the phase problem for neutron reflectivity that allowed the direct

inversion of the reflection amplitude to obtain the scattering length 

density profile uniquely within the dynamical theory of diffraction. This

method involves the use of a layer, a substrate, or fronting material that

can be used as a reference, and is of immense importance for neutron

reflectivity studies of unknown structures. 

TANER YILDIRIM WINS NIST BRONZE MEDAL

NIST has recognized the work of Dr.

Taner Yildirim, physicist at the NCNR,

with a Bronze Medal award. Dr. Yildirim’s

theoretical research has led to a new

understanding of how the physical and

chemical properties of carbon nanotubes

can be controlled with pressure. He predicted that networks of covalently interlinked nanotubes would form under

pressure, a finding with clear implications

for the strength of nanocomposites that was later confirmed experimentally. He showed that compressing an insulating nanotube allows the

reversible tuning of the band gap, a critical property in nanoscale electronic devices, and could also be used to tune the chemical reactivity at

specific sites on the nanotubes, allowing attachment of selected atoms to

those sites. This latter prediction holds promise for controlled nanochemistry and chemical filtering.

Neutron Research with Silver

Medal awards. Drs. Krueger,

Dura, Majkrzak and Mr. Pierce are

recognized for their outstanding

scientific and engineering leadership in establishing, at the NCNR,

the Cold Neutrons for Biology

and Technology (CNBT), a partnership between 

Institutes of Health, and six major U.S. universi

partners conceived, developed, and implemente

tron diffraction and reflection instrumentation, 

structural biology research that provides the Un

new capabilities for future studies of key biolog

RABINOW AWARD MADE TO PAUL BR

FIELDS AND HENRY PRASK

Drs. Pau

Richard 

MSEL) a

(NCNR) 

Rabinow 

by NIST

Drs. Bra

have dev

capabili

stress depth profiles and texture in metals, ceram

They forged applied research collaborations with 

organizations, the Army and Navy, the Departm

and Energy, and 10 major universities. Their wo

impact on automobile spring production, sheet-

and machining technology as well as advanced 

Their measurement of residual stress in railroad 

portation infrastructure and has facilitated majo

ing of mechanical properties of materials. 

56
associated with regular membership.

FRANK BATES PRESENTED TURNBULL LECTURE AWARD

Dr. Frank Bates, Distinguished McKnight University Professor and 

Head of Chemical Engineering and Materials Science at the University 

of Minnesota, was presented the

Turnbull Lecturer Award at the

2004 MRS Fall Meeting in Boston.

The Award recognizes the career 

of a scientist who has made outstanding contributions to understanding materials phenomena and

properties through research, writing, and lecturing, as exemplified

by David Turnbull. 

“For pioneering contributions to the fundamental understanding of structure and properties of complex polymeric materials, particularly block copolymers and polymeric

vesicles, coupled with outstanding lecturing, writing,

teaching, and educational leadership.”

Professor Bates has been a frequent visitor to the NCNR using neutrons

to study polymer structure on the NG-7, 30 m SANS instrument that is

funded by a Participating Research Team that includes the University of

Minnesota. He was awarded the 1997 Polymer Physics Prize by the

American Physical Society and was elected to the US National Academy

of Engineering in 2002.

THOMAS RUSSELL AWARDED 

2005 POLYMER PHYSICS PRIZE

Dr. Thomas Russell, Distinguished Professor of the P

& Engineering Department of the University of Mass

and a frequent user of facilities at the NCNR was awa

Polymer Physics Prize...

“for his pioneering research and fundamen

elucidation of the surface and interfacial 

of polymers”. 

The prize consists of $10 000 and a

certificate citing the contributions

made by the recipient. It was presented to Professor Russell at the

American Physical Society March

2005 meeting in Los Angeles, CA.

Professor Russell is Director of the

Materials Research Science and

Engineering Center on Polymers,

Associate Director of MassNanoTech, and is an Assoc

Macromolecules. He is a fellow of the American Phys

American Association for the Advancement of Scienc

elected Distinguished Professor, and was given the D
, 

p,

Proceedings of the XI International Workshop on Neutrino Telescopes, edited by Baldo-Ceolin, M., (February, 2005, Venice, Italy) p. 76 (2005).

Adams, C. P., Lynn, J. W., Smolyaninova, V. N., Biswas, A., Greene, R. L., 

Ratcliff, W., Cheong, S.-W., Mukovskii, Y. M., Shulyatev, D. A., “FirstOrder Nature of the Ferromagnetic Phase Transition in (La-Ca)MnO3

Near Optimal Doping,” Phys. Rev. B 70, 134414 (2004).

Aharony, A., Entin-Wohlman, O., Korenblit, I. Y., Harris, A. B., Yildirim, 

T., “The Cubic Kugel-Khomskii Model for Triply Degenerate t2g

Electrons,” New J. Phys. 7, 49 (2005).

Akcora, P., Zhang, X., Varughese, B., Briber, R. M., Kofinas, P., “Structural 

and Magnetic Characterization of Norbornene-Deuterated Norbornene

Dicarboxylic Acid Diblock Copolymers Doped With Iron Oxide

Nanoparticles,” Polymer 46 (14), 5194 (2005).

Aldrige, L. P., Bordallo, H. N., Desmedt, A., “Water Dynamics in Cement 

Pastes,” Physica B 359, E565 (2004).

Alinger, M. J., Odette, G. R., Hoelzer, D. T., “The Development and 

Stability of Y-Ti-O Nanoclusters in Mechanically Alloyed Fe-Cr Based

Ferritic Alloys,” J. Nucl. Mater. 329-333, 382 (2004).

Allen, A. J., “Characterization of Ceramics by X-Ray and Neutron SmallAngle Scattering,” J. Am. Ceram. Soc. 88 (6), 1367 (2005).

Allen, A. J., McLaughlin, J. C., Neumann, D. A., Livingston, R. A., “In 

Situ Quasielastic Scattering Characterization of Particle Size Effects on

the Hydration of Tricalcium Silicate,” J. Mater. Res. 19, 3242 (2004).

Alvarez, E., Lindstrom, R. M., Paul, R. L., Cook, J., Schröder, I. G., 

“Redesign of the Cold-Neutron Analytical Chemistry Instruments at

the NIST Center for Neutron Research,” Transactions of the American

Nuclear Society 91, 823 (2004).

Anderson, D. L., Cunningham, W. C., “Analysis of Total Diet Study Foods 

for Gamma-Ray Emitting Radionuclides,” J. Radioanal. Nucl. Chem.

Lett. 264 (2), 371 (2005).

Anderson, D. L., Kastovszky, Z. S., “Applications of PGAA with Beams,” 

Chapter 6, in Handbook of Prompt Gamma Activation Analysis with

Neutron Beams, edited by Molnár, G. L. (Kluwer Academic Publishers,

Netherlands), p. 137 (2004).

Anderson, D. L., Mackey, E. A., “Improvements in Food Analysis by 

Thermal Capture Prompt Gamma-Ray Spectrometry,” J. Radioanal.

Nucl. Chem. Lett. 263 (3), 683 (2005).

Argyriou, D. N., Ruett, U., Adams, C. P., Lynn, J. W., Mitchell, J. F., 

“Phase Separation Without Quenched Disorder in Pr0.7Ca0.3MnO3,”

New J. Phys. 6, 195 (2004).

Balzar, D., Audenbrand, N., Daymond, M. R., F

Langford, J. I., LeBail, A., Louër, D., Masson, 

Popa, N. C., Stephens, P. W., Toby, B. H., “Siz

Analysis of the Ceria Round-Robin Sample,” J

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Bandyopadhyay, R., Liang, D., Yardimci, H., Ses

M. A., Mochrie, S. G. J., Harden, J. L., Lehen

Particle-Scale Dynamics in an Aging Clay Sus

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Snow, W. M., Mumm, H. P., Nico, J. S., Huffm

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Garcia-Sakai, V., Chen, C., Maranas, J. K., Chowdhuri, Z., “Effect of 

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Gehring, P. M., Copley, J. R. D., “NCNR Holds Eleventh Annual Summer 

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Lauss, B., Leuschner, M., Losowski, B., Hauri

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Gilliam, S. B., Gidcumb, S. M., Parikh, N. R., Pa

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Gnäupel-Herold, T., Foecke, T., Prask, H. J., Fie

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60
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Hamilton, W. A., Porcar, L., Magid, L. J., “Using Neutron Relectometry 

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Hauer, B., Hempelman, R., Udovic, T. J., Rush, J. J., Kockmann, W., 

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Hiraka, H., Böni, P., Yamada, K., Park, S., Lee. S.-H., Shirane, G., 

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Hiraka, H., Lee, S.-H., Gehring, P. M., Xu, G., Shirane, G., “Cold Neutron 

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J. Phys.: Condens. Matter 16, 5803 (2004).

Huang, Q., Foo, M. L., Pascal, R. A., Lynn, J. W., Tob

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Hubbard, F. P., Santonicola, G., Kaler, E. W., Abbott, 

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Hücker, M., Kim, Y. J., Gu, G. D., Tranquada, J. M., G

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Hudson, B. S., Braden, D. A., Allis, D. G., Jenkins, T.

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Hussey, D. S., Jacobson, D. L., Arif, M., Huffman, P. R

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Hussey, D. S., Rich, D. R., Belov, A. S., Tong, X., Yang

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Jacob, R. E., Teter, J., Saam, B., Chen, W. C., Gentile, T. R., “Low-Field 

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Jeng, U. S., Hsu, C. H., Lin, T. L., Wu, C.-M., Chen, H.-L., Tai, L.-A., 

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Jeong, H. K., Krych, W., Ramanan, H., Nair, S., Marand, E., Tsapatsis, 

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Jones, C. Y., Luecke, W. E., Copland, E., “Neutron Diffraction Study of 

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Physica B 356 (1-4), 86 (2005).

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Kirby, B. J., Borchers, J. A., Rhyne, J. J., O’Dono

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68
tg-h@nist.gov 

V. Luzin, (301) 975-5303, luzin@nist.gov

30-M SANS INSTRUMENT (NG-7): 

L. Porcar, (301) 975-5049,

lionel.porcar@nist.gov

P.D. Butler, (301) 975-2028, butler@nist.gov 

J.G. Barker, (301) 975-6732,

john.barker@nist.gov

J. Krzywon, (301) 975-6650,

jeffery.krzywon@nist.gov 

30-M SANS INSTRUMENT (NG-3)

(CHRNS):

B. Hammouda, (301) 975-3961,

hammouda@nist.gov 

S.R. Kline, (301) 975-6243,

steven.kline@nist.gov 

D. Ho, (301) 975-6422, derek.ho@nist.gov

B. Greenwald, (301) 975-5797, 

bryan.greenwald@nist.gov

USANS, PERFECT CRYSTAL 

SANS (BT-5) (CHRNS):

J.G. Barker, (301) 975-6732,

john.barker@nist.gov 

M.-H. Kim, (301) 975-6469, 

man-ho.kim@nist.gov 

P.D. Butler, (301) 975-2028, butler@nist.gov

COLD NEUTRON REFLECTOMETERVERTICAL SAMPLE-POLARIZED BEAM

OPTION (NG-1):

C.F. Majkrzak, (301) 975-5251,

cmajkrzak@nist.gov 

J.A. Dura, (301) 975-6251, jdura@nist.gov

ADVANCED NEUTRON DIFFRACTOMETER/

REFLECTOMETER (NG-1):

U. Perez-Salas, (301) 975-8395, ula@nist.gov

K. O’Donovan, (301) 975-8380, 

kevin.odonovan@nist.gov

COLD NEUTRON REFLECTOMETERHORIZONTAL SAMPLE (NG-7): 

S.K. Satija, (301) 975-5250, satija@nist.gov

S. Basu, (301) 975-5192, saibal.basu@nist.gov

SPINS, SPIN-POLARIZED TRIPLE-AXIS

SPECTROMETER (NG-5) (CHRNS): 

J.-H. Chung, (301) 975-8369, 

jae-ho.chung @nist.gov 

H.-J. Kang, (301) 975-4863, hye.kang@nist.gov 

FANS, FILTER-ANALYZER NEUTRON

SPECTROMETER (BT-4): 

T.J. Udovic, (301) 975-6241, udovic@nist.gov

J. Leao, (301) 975-8867, juscelino.leao@nist.gov 

DCS, DISK-CHOPPER TIME-OF-FLIGHT

SPECTROMETER (NG-4) (CHRNS):

J.R.D. Copley, (301) 975-5133, jcopley@nist.gov 

Y. Qiu, (301) 975-3274, yiming.qiu@nist.gov

C.M. Brown, (301) 975-5134,

craig.brown@nist.gov

HFBS, HIGH-FLUX BACKSCATTERING

SPECTROMETER (NG-2) (CHRNS): 

E. Mamontov, (301) 975-6232,

mamontov@nist.gov

V. Garcia Sakai, (301) 975-4404, vicky@nist.gov

NSE, NEUTRON SPIN ECHO 

SPECTROMETER (NG-5) (CHRNS): 

A. Faraone (301) 975-5254,

antonio.faraone@nist.gov 

PROMPT-GAMMA NEUTRON 

ACTIVATION ANALYSIS (NG-7): 

R.M. Lindstrom, (301) 975-6281, 

dick.lindstrom@nist.gov 

R.L. Paul, (301) 975-6287, rpaul@nist.gov

THERMAL NEUTRON PROMPT-GAMMA

ACTIVATION ANALYSIS (VT-5):

E.A. Mackey, (301) 975-5149,

liz.mackey@nist.gov

OTHER ACTIVATION ANALYSIS FACILITIES: 

R.R. Greenberg, (301) 975-6285,

rgreenberg@nist.gov 

COLD NEUTRON DEPTH PROFILING (NG-0):

G. Downing, (301) 975-3782, 

gregory.downing@nist.gov 

FUNDAMENTAL NEUTR

STATION (NG-6): 

NG-6M: M.S. Dewey, (301

mdewey@nist.gov 

NG-6U: H.P. Mumm, (301) 

pieter.mumm@nist.gov

NG-6: J. Nico, (301) 975-4

THEORY AND MODELIN

T. Yildirim, (301) 975-622

N.F. Berk, (301) 975-6224

SAMPLE ENVIRONMEN

J. Leao, (301) 975-8867, ju

D.C. Dender, (301) 975-62

NIST CENTER FOR NE

RESEARCH

For copies of or informati

report, contact:

Ronald L. Cappelletti 

301-975-6221 

ron.cappelletti@nist.gov

For additional informatio

facility, contact:

Patrick D. Gallagher

301-975-6210

patrick.gallagher@nist.gov

Dan A. Neumann

301-975-5252

dan.neumann@nist.gov

To obtain guidelines for p

to conduct research at th

William A. Kamitakahara

301-975-6878

william.kamitakahara@nist.g

Location of all contacts:

NIST Center for Neutron R

National Institute of Stand

100 Bureau Drive, Mail Sto

Gaithersburg, MD 20899

Copies of this report and o

available electronically. Plea

www.ncnr.nist.gov