## Research Activity: Theoretical Condensed Matter Physics

Division: Materials Sciences and Engineering

Primary Contact(s): Manfred Leiser
([Manfred.Leiser@Science.DOE.gov](mailto:Manfred.leiser@Science.DOE.gov)
301-903-4894)

Team Leader: William Oosterhuis

Division Director: Iran Thomas

**Portfolio Description:**

The Theoretical Condensed Matter Physics activity provides theoretical
support for all parts of the Materials Science and Engineering Division.
Research areas include quantum dots, nanotubes and their properties,
tribology at the atomic level, superconductivity, magnetism, and optics.
A significant part of the portfolio consists of the development of
advanced computer simulation algorithms and fast codes to treat
many-particle systems. An important component of the portfolio is the
Computational Materials Science Network (CMSN), which brings together
groups of scientists from DOE laboratories, universities, and (to a
lesser extent) industry to solve materials problems requiring
collaboration across disciplinary and organizational boundaries.

**Unique Aspects:**

The rapid advance in technological and computational capabilities makes
it possible to perform research in condensed matter theory and materials
science at an unprecedented level of sophistication. The resulting
complexity of the research requires an increasing diversity of
disciplines. Consistent with the increasing acceptance of computational
science as a "third way of doing science" the activity includes the
Computational Materials Science Network. The CMSN is a unique program
that brings together a multi-disciplinary group of scientists from DOE
laboratories, universities, and industry to collaborate on computational
materials science projects. At present CMSN consists of five
sub-projects: Excited State Response Functions (testing the accuracy of
current levels of fundamental theory); Microstructural Effects on the
Mechanics of Materials (computational study of the fundamental basics of
metallurgy); Microstructural Evolution Based on Fundamental Interfacial
Properties (a fundamental factor to understand the processing of real
materials); Polymers at Interfaces (a study of failure modes since this
region is the weakest link in composite materials); Magnetic Materials
Bridging Basic and Applied Science (an attempt to interconnect different
scales of magnetic behavior from quantum mechanical electronic behavior
al the way to continuum micro-mechanical properties). Other projects
will be considered including electronic structure techniques tailored
specifically to nanoparticles, polymer matrixing, and complex
correlation issues.

**Relationship to Others:**

Within DOE a high level of collaboration exists between MICS and NERSC.
Information on university grants is shared with NSF, peer reviews are
sometimes shared, and on occasion there is joint funding of grants. On
the international level participation in organizing and steering
committees is frequent, as are exchanges of experts between foreign and
domestic institutions.

**Significant Accomplishments:**

Consistent with the emphasis on nanoscience enabled by developments in
technology and computational techniques, notable achievements in this
area have been made within the Condensed Matter Theory Activity.

Research into low dimensional materials has revealed exciting new
information and has pointed to new possibilities in creating new
tailored materials and devices. Highlights include:

1.  The discovery that magnetization around defects in quasi-one
    dimensional materials greatly influences the phase in which they
    reside points to the development of sensors highly sensitive to
    external stimuli.

2.  The discovery that loading electrons into quantum dots results in
    the formation, within the dot, of complexes of holes and electrons.
    These decay in a theoretically predictable manner, pointing to the
    possibility of fabricating quantum dots with tailored light emitting
    properties.

3.  The discovery that electrons confined in a thin film segregate into
    discreet energy levels, in analogy to the discreet energy levels in
    atoms, points to the possibility of constructing ultra-stable
    materials by controlling the thickness of the film.

4.  Calculations show that the conductance across two crossed carbon
    nanotubes is very sensitive to the force applied at that junction.
    While the inter-tube conductance is dramatically increased, the
    intra-tube conductance is diminished. When this arrangement is
    realized experimentally, crossed nanotubes can be expected to be
    excellent sensors for applied forces within nanoscaled devices.

Significant progress has also been made in other areas as illustrated by
the following examples.

Dynamic mean-field theory, which is exact for infinite dimensions, has
been successfully coupled with three dimensional band theory. The
resulting hybrid theory predicts the anomalous properties of highly
correlated rare-earth and actinide materials.

When metals solidify they form highly branched patterns called
dendrites. These solidification patterns control many aspects of
processing and microstructure and hence our ability to use materials. A
Collaborative Research Team of the Computational Materials Science
Network has devised an entirely new method for extracting the anisotropy
of energy and mobility responsible for dendrite formation from
supercomputer simulations of the atomic processes occurring during
solidification.

*Ab initio* calculations have been performed for the hysteresis loop and
domain wall dynamics of magnets. Long thought to be beyond the scope of
*ab initio* calculations because of the large number of atoms involved,
it became possible to perform detailed studies of some less demanding
materials such as FePt and CoPt, which are technologically important.

**Mission Relevance:**

The program's ultimate purpose is to understand the properties of
existing materials and to create new ones that are more efficient in
producing, storing, and using energy. To this end, the programs in this
portfolio have the common goal of achieving a basic understanding of
matter ranging from the atomic to the bulk scales. The experimental and
theoretical programs work in close collaboration with each other, but
more independent modes of research also exist. Theorists will try to
establish a theoretical basis for experimentally observed results, which
almost always suggests further experiments, and thus leads to new
results. New science is produced by simulating processes on computers,
"computer experiments" which are difficult or impossible perform in the
laboratory. The behavior of the surface layers of materials sliding on
each other and a new understanding of the role of lubricants has been
obtained in this way. Other examples include investigations into the
behavior of electrons flowing in nano wires and nanotubes and in the
properties of matter at extreme conditions of temperature and pressure.

**Scientific Challenges:**

Because of the close relationship between the experimental and
theoretical elements, many of these are common to both. Examples of
areas common to both are exploring the behavior of complex systems,
investigating nano-scale systems, and understanding superconductivity.
In theory, the need to develop functionals defined by the Density
Functional Theory and needed for its applications is an example as is
the need to develop more efficient algorithms for the efficient use of
modern computers.

**Funding Summary:**

**Dollars in Thousands**

**[FY 2000]{.underline}** **[FY 2001]{.underline}** **[FY
2002]{.underline}**

\$14,888 \$16,124 \$18,116

> **[Performer]{.underline} [Funding Percentage]{.underline}**
>
> DOE Laboratories 79.0%
>
> Universities 21.0%

The program provides funding for 47 university grants supporting about
as many students and partially supporting about 50 faculty and senior
staff and programs at 9 national laboratories. There are approximately
70 postdocs fully or partially supported by this CRA. Programs at the
laboratories are multi-investigator efforts on problems that require
extensive participation experimental and theoretical scientists. This
program supports research at LBNL, AMES, BNL, ANL, LLNL, MRS, LANL,
ORNL, and NREL. Many of the research efforts at national laboratories
involve interfaces with the university and industrial communities and
user facilities. In addition, about \$1.4M on is provided to projects of
the Computational Materials Science Network.

**Projected Evolution:**

Rapid advancements in computer hardware and software will be exploited
to model materials with ever-greater sophistication and realism. The
ability to perform experiments at the nanoscale and similar advances in
computational technology (software and hardware) has opened a new era in
materials science. It is expected that increasing emphasis will be
placed on nanoscience studies. For the theory program, this will
necessitate an even tighter coupling between theory and experiment.

04 February 2002