bluuebunny/crossref_metadata_2025 huggingface dataset:
A combined high-pressure diffraction and computational study on scandium MOFs
Authors: Moggach Stephen , Graham Alexander , Banu Ana-Maria , Düren Tina , Greenaway Alex , McKellar Scott , Mowat John , Ward Kenneth , Wright Paul
Published: November 2015

Previous high-pressure experiments have shown that pressure-transmitting fluids composed of small molecules can be forced inside the pores of metal organic framework materials, where they can cause phase transitions and amorphization and can even induce porosity in conventionally non-porous materials.1 Here we present a combined high-pressure diffraction and computational study of the structural response to methanol uptake at high pressure on a scandium terephthalate MOF (Sc2BDC3, BDC=1,4-benzenedicarboxylate)2 and its nitro-functionalized derivative (Sc2(NO2-BDC)3)3 and compare it to direct compression behaviour in a non-penetrative hydrostatic fluid, Fluorinert-77. In Fluorinert-77, Sc2BDC3 displays amorphization above 0.1 GPa, reversible upon pressure release, whereas Sc2(NO2-BDC)3 undergoes a phase transition (C2/c to Fdd2) to a denser but topologically-identical polymorph. In the presence of methanol, the reversible amorphization of Sc2BDC3 and the displacive phase transition of the nitro-form are completely inhibited (at least up to 3 GPa). Upon uptake of methanol on Sc2BDC3, the methanol molecules are found by diffraction to occupy two sites, with preferential relative filling of one site compared to the other: grand canonical Monte Carlo simulations support these experimental observations and molecular dynamics simulations reveal the likely orientations of the methanol molecules, which are controlled at least in part by H-bonding interactions between guests. As well as revealing the atomistic origin of the stabilization of these MOFs against non-penetrative hydrostatic fluids at high pressure this study demonstrates a novel high pressure approach to study adsorption within a porous framework as a function of increasing guest content, and so to determine the most energetically favourable adsorption sites.
Assessing and predicting flexibility in MOFs with molecular simulation
Authors: Coudert Francois-Xavier
Published: November 2015

Much attention has recently been focused flexible metal-organic frameworks (MOFs), or Soft Porous Crystals, that behave in a remarkable stimuli-responsive fashion upon guest adsorption, temperature, or mechanical pressure. It was shown that these different stimuli-driven structural transitions can be rationalized by combining an understanding of adsorption thermodynamics and mechanical properties of the host phases. We will show how the combination of a large range of molecular simulation methods can assess the extent of flexibility of known MOF structures, as well as give physical insight into their deformation mechanisms, and predict the occurrence of new phases. In particular, we will demonstrate the breathing nature of recently synthesized MOFs CAU-13 and NOTT-300, that have not been observed experimentally.
Crystal Structures Of Several Inorganic-Organic Hybrids Solved From Powder XRD
Authors: Djerdj Igor , Kozlevcar Bojan , Kitanovski Nives , Rocquefelte Xavier , Popovic Jasminka , Nuskol Marko , Moliterni Anna Grazia , Altomare Angela
Published: November 2015

When dealing with the crystal structure solving of low-crystalline materials, it is of paramount importance to combine DFT geometry optimization with direct-space methods in order to find the correct structural model. Particularly, in the case of inorganic-organic hybrids prepared by solvothermal route, finite dimensional single crystal is very difficult to obtain. Hence, we present several successfully elucidated crystal structures from the powder XRD of the low-crystalline inorganic-organic hybrids: Cr(HL)Cl3, HL=Hbdmpza (1), [1] VO(C10H7COO)2 (2), VO(C14H9COO)2 (3). All of these structures have been solved from powder XRD data, either from laboratory or synchrotron source, by combining direct-space methods (simulated annealing), DFT geometry optimization, and constraint Rietveld refinement. The solid compound 1 was isolated in acetonitrile by starting CrCl3·9H2O and HL only in a concentrated solution, from which microcrystalline aggregates precipitated. Additionally, the presence of a carboxylate proton in HL stabilizes the structure by H-bonds, but also enables adsorption of moisture. Other two hybrids were synthesized in o-xylene by reacting vanadium (V) triisopropoxide with 1-naphthalenecarboxylic [2] or 9-anthracenecarboxylic acid. [2] They contain one-dimensional chain of corner-sharing tetrahedra in the case of VO(C10H7COO)2 (Figure 1(a), (c)), and corner-sharing octahedra for VO(C14H9COO)2 (Figure 1(b), (d)) oriented along orthorhombic/monoclinic c-axis, respectively. While VO(C14H9COO)2 exhibits bidentate bridging binding of organic moiety to the metal center, VO(C10H7COO)2 shows monodentate mode as evidenced from DFT and infrared spectroscopy. The obtained crystal structures were further verified by direct methods (ab initio approach). I. D. acknowledges financial support from the Unity through Knowledge Fund (www.ukf.hr) of the Croatian Ministry of Science, Education and Sports (Grant Agreement No. 7/13).
Structural analysis of crystal surfaces of flexible metal-organic frameworks
Authors: Furukawa Shuhei , Kitagawa Susumu
Published: November 2015

Structural transformability accompanied with molecular accommodation is a distinguished feature of metal-organic frameworks among porous materials. Conventional X-ray crystallography allows for the determination of each structural phase emerged during transformation. However, the propagation mechanism of transformation through an entire crystal still remains in question. Here we elucidate the structural nature of spatial transient state, in which two different but correlated framework structures, an original phase and a deformed phase, simultaneously exist in one crystal. The deformed phase is distinctively generated only at the crystal surface region by introducing large guest molecules, whilst the remaining part of crystal containing small molecules maintains the original phase. By means of grazing incidence diffraction techniques we determine that the framework is sheared with sharing one edge of the original primitive cubic structure, leading to the formation of crystal domains with four mirror image relationships.
Crystal chemistry of layered Pb oxyhalides: crystal structure of Pb3[Pb20O10](GeO4)Cl10
Authors: Zinyakhina Diana , Siidra Oleg , Zadoya Anastasiya , Krivovichev Sergey , Turner Rick
Published: November 2015

Pb oxyhalides are of interest due to their environmental and technological importance. They are also known as important constituents of oxidation zones of mineral deposits. Most Pb oxyhalides have layered α-PbO-derivative structures, which are related to the Aurivillius phases. The crystal structures of Pb-O related layered lead oxyhalides are based upon the O–Pb layers alternating with the X sheets of X– ions (X = Cl, Br, I). The PbO-derivative compounds may also incorporate a wide range of elements, including As, S, V, Mo, W, P, Si, etc., which results in interesting chemical and structural diversity and complexity. Pb3[Pb20O10](GeO4)Cl10(1) was obtained by rapid quenching of lead-oxyhalide melt [1]. The structure of 1 (Cmca, a = 28.352(19), b = 11.116(7), c = 16.513(11) Å, V = 5204(6) Å3, R1 = 0.0504) contains 7 symmetrically independent Pb sites. Pb(6) site is splitted into less occupied Pb6A and Pb6B sites. The coordination environments of the Pb atoms are variable in agreement with the presence of stereochemically active "lone pairs" on divalent lead cations. The structure of 1 contains one Ge site coordinated tetrahedrally by four O atoms with the average  bond length equal to 1.75 Å. The total number of oxygen sites is seven. The O(3), O(4), O(6), and O(7) sites are bonded to Ge, whereas other O atoms (O(1), O(2), O(5)) are tetrahedrally coordinated by Pb atoms, which results in formation of oxocentered OPb4tetrahedra. 1 belongs to the 1:1 type and consists of alternating PbO-type layers and mixed Pb–Cl sheets oriented parallel to (100). The PbO-type layer is a derivative of the [OPb] tetrahedral layer in α-PbO and can be obtained from the latter by removal of blocks of oxocentered tetrahedra. The GeO4tetrahedral anions locate in the cavities within the PbO-type layer. The formula of the layer can be written as [O10Pb20]2°+. The structure of 1 illustrates the complexity of the lead oxyhalide systems and validates new pathways for synthesis of complex Pb oxyhalides.
Mesoporous Metal Phosphites with 3D Crystalline Frameworks
Authors: Wang Sue-Lein
Published: November 2015

The synthesis of crystalline porous solids is of great importance in the area of materials chemistry. Naturally occurring zeolites are mostly crystalline; however, they possess pores/channels that only allow small species smaller than 1 nm in diameter to pass through. One exception is the mineral cacoxenite, containing 36-membered ring (36R) channels that allow guest species of up to 1.41 nm in diameter to pass through. In the past, much effort has been devoted to the development of zeolitic materials. Even though multi-faceted design strategies were utilized, the discovery of larger inorganic channels was often accidental. Compared with amorphous mesoporous silicates that contain synthetically tunable pores, zeolitic crystalline structures lack rational synthesis routes. In general, molecular templating leads to crystalline frameworks whereas organized assemblies that are able to produce much larger pores lead to noncrystalline frameworks. Synthetic methods that generate crystallinity from both discrete and organized templates represent a viable design strategy for the development of crystalline porous inorganic frameworks spanning both the micro and the meso regimes. We show by integrating templating mechanisms for both zeolites and mesoporous silica in a single system, the channel size for gallium zincophosphites can be tuned systematically up to 64R and 72R. With apertures of 3.5 nm, the new compounds represent the first non-disordered structures for mesoporous solids. Through the use of long straight-chain alkyl monoamines as templates, three common building blocks are induced that repeatedly self assemble into two isotypic porous frameworks with the ability to increasingly enlarge channel size. The rational design of crystalline porous metal oxides is achieved for the first time. A general formula was derived to predict new members with even larger channels along with their individual space group symmetry.
Bond valence constraints on the composition of 3d-elements bearing tourmalines
Authors: Vereshchagin Oleg , Frank-Kamenetskaya Olga , Rozhdestvenskaya Ira
Published: November 2015

F.C. Hawthorne (2002) and F. Bosi (2011) showed that bond valence approach is to be applied to stability prediction of tourmaline structure with different chemical composition. Using this approach we considered bond valence constraints on occupation of Y, Z, V and W sites of Cu-, Ni-bearing tourmalines. From the standpoint of the bond valence approach, [3YW] unit is unstable if W site is fully occupied by O2-. The stability of [3YW] unit decreases along a row: 3 divalent cations → 2 divalent cations + 1 trivalent cation → 2 trivalent cation + 1 divalent cations → 3 trivalent cations if W site is fully occupied by OH- or F-. There is no limitation on 3d elements and aluminum content in [2ZYV] if V site is fully occupied by OH-. The [2ZYV] unit is unstable if V site is fully occupied by O2-. The data, obtained from calculation of bond valences are in a good agreement with results of single crystal structure refinements of synthetic Cu- (Ertl et al., 2013) and Ni-tourmalines: Cu-bearing olenite with a CuO content of 8.39 wt.% [a = 15.849(1), c =7.087(1) Å, R = 2.5%] and Ni-bearing olenite with a NiO content of 18.96 wt.% [a = 15.890(2), c = 7.1815(8), R = 3.1%]. In all cases W and V sites are predominantly occupied by OH- anions. The composition of [3YW] units are [(Cu1.80Al1.20)(OH)0.60F0.40] and [(Ni1.80Al1.20)(OH)1.00]. Breaking of charge balance with increasing of bivalent cations is maintained by increasing of portion of vacancies at X site and increasing of content of trivalent cations (Al, B) at T site.
Unusual crystal structures in the system (SnSe)nBi2Se3
Authors: Urban Philipp , Fraunhofer Christina , Fahrnbauer Felix , Wagner Gerald , Oeckler Oliver
Published: November 2015

As intermediates between layered tellurides and chain-like sulfides, selenides exhibit a huge variety of structures and are promising candidates for thermoelectrics. The compounds (SnSe)nBi2Se3 cover the whole range of compound classes. (SnSe)0.5Bi2Se3 exhibits the 21R-GeSb2Te4 structure type (R-3m, a = 4.172Å, c = 38.86 Å, R1(obs) = 0.0246) [1] instead of the 12P stacking expected for this stoichiometry, HRTEM indicates the presence of stacking disorder. This phase coexists with "phase X" [2]. From such samples, e.g. (SnSe)~2Bi2Se3, single crystals of new compounds could be retrieved. Their structures resemble those of minerals of the lillianite series. Slowly cooled samples near the dystectic composition [2] in the phase diagram yielded lillianite-type (SnxBi1-x)5Se6 (x ≍ 2, Cmcm, a = 4.196 Å, b = 13.83 Å, c = 21.19 Å, R1(obs) = 0.0347) mixed with (SnxBi1-x)11Se13 (x ≍ 3, C2/m, a = 13.85 Å, b = 4.205 Å, c = 23.33 Å, β = 98.70, R1(obs) = 0.0594), which is isotypic to KSn5Bi5Se13 [3]. Further a new phase (SnxBi1-x)8Se9 with heyrovskite-type structure (x ≍ 3, Cmcm, a = 4.193 Å, b = 13.87Å, c = 32.01 Å, R1(obs) = 0.0392) was obtained. These new structures consist of tropochemically twinned slabs that represent distorted cutouts of the rocksalt type. They are interconnected via cations in trigonal prisms. They are members of a homologous series that differ concerning the thickness of the slabs. The cubic high-temperature phase (SnSe)nBi2Se3 (~2.5 < n < 4) yields a metastable pseudocubic disordered rocksalt-type material (Fm-3m, a = 5.936 Å, R1(obs) = 0.0473) upon quenching. For n = 4, it contains homogeneously distributed nanoscale SnSe precipitates. Such a heterostructure might explain the low thermal conductivity (0.83 Wm-1K-1 at room temperature). The rather low electrical conductivity might be further tuned by substitution, which promises an intriguing approach for new nanostructured thermoelectrics easily accessible by partial phase transitions and exsolution effects.
Nanoindentation and ellipsometry of Li2ZnTi3O8& Zn2TiO4single crystals
Authors: Perfler Lukas , Kahlenberg Volker , Wikete Christoph , Kaindl Reinhard
Published: November 2015

Spinel-type Li2ZnTi3O8and Zn2TiO4are useful for various industrial applications due to their interesting chemical and physical properties, for example, as promising anode materials in Li-ion batteries or as components in dielectric devices [1]. Since Li2ZnTi3O8and Zn2TiO4are expected to have high refractive indices (n calc. = 2,33 and 2,26) we tried to characterize these materials in more detail including single-crystal X-ray diffraction, nanoindentation, spectroscopic ellipsometry and electron microprobe analysis. Single crystals of Li2ZnTi3O8and Zn2TiO4were grown directly from melt at 1723 K and 1873 K, respectively. Fragments of sintered polycrystalline Li2ZnTi3O8and Zn2TiO4precursors were placed on an iridium sheet and fired in a muffle furnace from 1273 to 1723/1873 K with a heating ramp of 15 K/min. After a dwell time of 3 min the melt was cooled down to 1473 K with a ramp of 10 K/min and subsequently quenched in water. Structural investigations of the Li2ZnTi3O8and Zn2TiO4single crystals resulted in the following basic crystallographic data: cubic, P4332, a = 8.3697(2) Å, V = 586.31(3) Å3, Z = 4 and Fd-3m, a = 8.46230(17) Å, V = 605.99(2) Å3, Z = 8, respectively. Nanoindentation experiments were performed with a Berkovich diamond indenter tip to determine the hardness and elastic modulus of Zn2TiO4and Li2ZnTi3O8. For sample preparation the single crystals were embedded in resin and polished to a mirror-like surface finish. More than 150 indents with a distance of 10 µm were made with a maximum load of 20 mN. Analysis of the load-displacement curves for Zn2TiO4revealed a hardness of 10.5110.39 GPa and a reduced elastic modulus of 180.9013.92 GPa. Atomic force micrographs displayed indents with a max. depth of 28815 nm. Li2ZnTi3O8exhibited a hardness of 6.8610.45 GPa and a reduced elastic modulus of 148.8816 GPa. Zn2TiO4showed a dispersion of 0.09 due to the variation of the refractive index from 2.24 (430,8 nm, Fraunhofer G line) and 2.15 (686,7 nm, B line).
Structure refinements of kottogite and symplesite solid-solution
Authors: Miyano Yumiko , Yoshiasa Akira , Sugiyama Kazumasa , Arima Hiroshi , Nakatani Tomotaka , Okube Maki
Published: November 2015

Kottogite and symplesite are zinc and ferrous arsenate minerals, respectively. These minerals make the Zn3-x,Fex(AsO4)2·8H2O solid-solution and belongs to the vivianite group of minerals with the chemical formula M3(TO4)2·8H2O. The structure of vivianite and symplesite were determined firstly by Mori and Ito, (1950). The structure of kottigite was refined by Hill, (1979). The strucrure of Zn1.63Fe1.37(AsO4)2·8H2O solid-solution crystallize in space group C2/m with a= 10.342(1), b= 13.484(2), c= 4.7756(5), β=105. 306(4), and Z=2. We performed the structure refinements of (Zn,Fe)3(AsO4)2·8H2O solid-solutions, Ojuela mine, Mapimi Durango, Mexico and Kiura mine, Ohita, Japan by RIGAKU single-crystal structure analysis system RAPID. The R and S values are around 0.03 and 1.08. We determined detail atomic coordinate and hydrogen atom positions. The hydrogen bonds were revealed based on hydrogen positions and bond valence caluculations. The octahedral edge-shareing M2O6(H2O)4 dimers and insular MO2(H2O)4 octahedra are linked by AsO4 terahedra. Two H2O group bonds to (Zn,Fe). Four hydrogen atoms are in the normal hydrogen bonds. Hydrogen atom positions have a tunnel structure and there is a path of proton-conduction and we conjecture that proton conductivity has large anisotropy of one direction. The related minerals, such as paradamite, legrandite and warikahnite have tunnel structure similar to vivianite group.
Growth and Characterization of Ce3+doped Calciumferrate(III) Type Crystals
Authors: Klimm Detlef , Philippen Jan , Guguschev Christo
Published: November 2015

Ce3+ ions in oxide hosts show broad optical emission in the green spectral range, because of a strong ligand field. Substances such as Ce3+ doped CaSc2O4 and SrY2O4 crystallizing in the calciumferrate(III) structure type are used as ceramic phosphors for white LED's. However, under ambient conditions cerium prefers the 4-valent state, e.g. CeO2. For the ceramics, charge compensation and incorporation of Ce3+ can be reached by adding alkaline oxides, where e.g. (Na+, Ce3+) are substituting (2 Ca2+). Unfortunately, this option is not feasible for single crystal growth from the melt, because at the very high melting points near 21000C (CaSc2O4, [1]) or even 22000C (SrY2O4, [2]) alkaline oxides are evaporating completely. It will be shown that nevertheless efficient Ce3+ doping of both hosts can be obtained if melt crystal growth is performed in a suitable atmosphere with sufficiently low oxygen fugacity. First crystal growth experiments where performed by LHPG (Laser Heated Pedestal Growth), but meanwhile bulk growth by the Czochralski technique is feasible too. The figure shows such Ce3+:CaSc2O4 single crystal. Especially Ce3+:CaSc2O4 shows efficient broad band green emission, and no foreign phases indicating Ce4+ (CeO2) can be detected by X-ray diffraction. TEM analysis hints on incorporation of Ce3+ on a Ca2+ site.
Uranyl selenates and sulfates: features of structure formation
Authors: Gurzhiy Vladislav , Krivovichev Sergey , Tananaev Ivan
Published: November 2015

Uranium compounds containing tetrahedral oxoanions are of special importance from the environmental and mineralogical points of view. In this work, we examine structural relations and systematics for uranyl compounds with tetrahedrally coordinated Se6+ and S6+ cations. The U6+ atoms is almost always present as approximately linear uranyl-ions [UO2]2+, that are coordinated by four, five or six additional anions in the equatorial plane. For the valence saturation of equatorial anions it is necessary to form additional chemical bonds, hence the uranyl polyhedra are usually polymerize with each other only through the equatorial vertices and edges, that results in prevalence of layered structures among the minerals and synthetic uranyl compounds. Analysis of uranyl selenate structures demonstrates predominance of structural connectivity based upon corner-sharing coordination polyhedra. Crystal structures of uranyl sulfates often based on edge-sharing heteropolyhedral units. In the crystal structures of inorganic uranyl compounds, uranyl selenate and uranyl sulfate complexes are linked via monovalent cations (K+, Na+, etc.) or octahedrally coordinated divalent cations ([Ni(H2O)6]2+, [Zn(H2O)6]2+, [Mg(H2O)6]2+, etc.). In the crystal structures of amine-templated uranyl compounds, structure formation is regulated by hydrogen bonding systems and by arrangement of hydrophobic and hydrophilic parts of molecules with voids and dense fragments of inorganic complexes. The basic structural principle of organic-inorganic uranyl composites templated by electroneutral molecules (such as crown ethers), is the translation of interactions between organic and inorganic components by means of protonated water molecule complexes (e.g., H5O2+ and H3O+). This work was supported by St. Petersburg State University and President of Russian Federation grant for young scientists (no. MK-1737.2014.5). XRD studies have been performed at the X-ray Diffraction Centre of St. Petersburg State University.
Survey of Bond Lengths in the Solid State for Oxides: Results and Applications
Authors: Gagne Olivier , Hawthorne Frank
Published: November 2015

A complete survey of bond lengths from the Inorganic Crystal Structure Database (ICSD) is presented for all atoms of the Periodic Table of Elements, bonded to oxygen and in different oxidation states and coordination numbers. From over 135,000 crystal structures, a total of 33,343 coordination polyhedra and 188,462 bond distances were collected after passing a rigorous filtering process. One hundred thirty-six (136) ions in four hundred seventy-three (473) different configurations (coordination numbers) resulted. First, the bondlength distributions are visually inspected. This leads to (1) the observation and visual interpretation of known phenomena (e.g. Jahn-Teller effect), and (2) the isolation of new phenomena, as trends that are less obvious in smaller case-studies become more noticeable. Next, different applications of the data are investigated. The completeness of the survey allows the reassessment of important parameters of the solid state: ionic radii, and bond-valence parameters. Of the 473 ionic radii derived in this study, 329 revisions are made to Shannon's list of radii [1] (of which 176 were estimates), and 144 new ionic radii are derived. Next, a systematic evaluation of all bond-valence parameters published to date is done for oxides. Furthermore, using a new method of derivation, 136 new pairs of bond-valence parameters are obtained. In comparison to the previous-best published bond-valence parameters, an overall average decrease in the r.m.s.d. to the valence-sum rule of 20.7% (12.6% when weighted) is observed for the 33,343 coordination polyhedra, using the new parameters. New equations to describe the bond-length to bond-valence relation are also investigated. From an optimization between the experimental and a priori bond-valences of 54 carefully-selected crystal structures, roughly 20 relatively simple equations were selected for testing. Following a rigorous evaluation, the current exponential equation was found to be a viable choice in describing the relation. Finally, bond-length and bond-valence ranges are assigned to the 473 configurations of the atoms. Whereas the bondlength ranges are a useful aid in structure refinement, the assignment of a bond-valence range to ions allows a priori analysis of site occupancy in crystal structures.
Crystal structure of a new lithium iron vanadate
Authors: Castro Laurent , Penin Nicolas , Carlier Dany , Wattiaux Alain , Pechev Stanislav , Darriet Jacques , Dollé Mickaël
Published: November 2015

Iron vanadates and phosphates have been widely explored [1-2] as possible electrode material for Li-ion batteries. In the goal of finding new materials, our approach was to consider existing materials and to investigate the flexibility of their network for possible substitutions. Among the different materials containing iron and vanadium, Cu3Fe4(XO4)6 (X = P, V) are isostructural to Fe7(PO4)6. Lafontaine et al. [3] discussed the structural relationships between β-Cu3Fe4(VO4)6 and several other vanadates, phosphates and molybdates of general formula AxBy(VO4)6. The interesting network flexibility was then demonstrated with the existence of four different crystallographic sites, which can be partially occupied depending on the x+y value : x+y = 7 for β-Cu3Fe4(VO4)6) and x+y = 8 for NaCuFe2(VO4)3. The LixFey(VO4)6 phase was then prepared considering the substitution of Li+ and Fe3+ for Cu2+ ions in β-Cu3Fe4(VO4)6 and the existence of an extra site to accommodate the charge compensation (7 ≤ x+y ≤ 8). As expected, a new lithium iron vanadate, isotructural to mineral Howardevansite was then obtained. Single crystal diffraction data were collected at room temperature on Enraf-Nonius CAD-4 diffractometer. Structure was refined with JANA-2006 program package. Mössbauer and magnetic measurements were also used to check the oxidation state of iron ions, to support the obtained crystal structure and to consider any possible structural/magnetic transitions. All the results will be presented and discussed in this presentation.
Unit Cell Determination of New Minerals by Using Electron Diffraction
Authors: Bekenova Galiya
Published: November 2015

Many new minerals recently discovered in Kazakhstan had platy (niksergievite), fiber (kazakhstanite) or fine powder (mitryaevaite) structural appearance. In monoclinic minerals with perfect or good (001) cleavage, d100 i d010-spacings in the hk0 zone could be measured on selected area electron-diffraction pattern from monocrystal tilted the way that axis c is parallel to the electron beam direction. This method was used for measuring d-spacings in new minerals such as kazakhstanite, niksergievite as well as in new discovered micas – sokolovaite and orlovite. In minerals with triclinic structure (mitryaevaite) the same method was used to determine d100, d010 as well as γ=1800-γ* (γ* is an angle between reciprocal lattice axes a* and b*). hk0-indices of each ring were defined by comparison of the normal texture (ring type) pattern and selected area pattern. For example, hk0-indices for triclinic cell of mitryaevaite were (010), (100), (-110), (110), (020) etc. When specimen with preferred orientation is tilted under angle φ toward electron beam, an "oblique texture" electron-diffraction pattern is obtained. Arcs of the ellipses on such diffraction pattern are formed by intersection of Ewald sphere with ring nodes. The height of the arc's maximum above the tilt axis is calculated by using the following formula: D=hp+ks+lq, where p, s, q are measured on the diffraction pattern [1-3]. For example, on "oblique texture" electron-diffraction pattern from vanalite with perfect (010) cleavage, arcs are merged with layer lines that intersect the ellipses and D=ks. Allocation of indices on texture electron-diffraction patterns from monoclinic niksergievite, sokolovaite and orlovite with perfect (001) cleavage is more difficult. In these cases, D= hp+lq. Heights of the arcs are situated symmetrical in regards to each lq level. With the help of "oblique texture" diffraction patterns stacking polytypes were indicated for such minerals.
High Pressure Diffraction for the Geosciences at the Advanced Light Source
Authors: Beavers Christine , Knight Jason , Kalkan Bora , Yan Jinyuan , MacDowell Alastair , Williams Quentin
Published: November 2015

The Advanced Light Source, in concert with COMPRES, supports a superconducting bending magnet beamline devoted to extreme conditions diffraction. This facility, beamline 12.2.2, is aimed at the geoscience community, but is available to any who desire high pressures, high temperatures and hard X-rays. The latest development has been integrating single crystal x-ray diffraction for diamond anvil cells into the existing suite of high pressure powder diffraction and amorphous scattering techniques. Multiple heating techniques are available to the user, as well as multiple detectors, which can be chosen to best suit the sample. The current staff are dedicated to improving the user friendliness of the beamline; a difficult experiment need not to be further complicated by a difficult beamline. Beamline infrastructure, including recent advances and improvements, will be discussed.
Hydration Study of Synthetic Yeelimite using LXRPD and SXRPD
Authors: Cuesta Ana , Alvarez Pinazo Gema , De la Torre Angeles , Sanfélix Susana , Peral Inmaculada , Aranda Miguel
Published: November 2015

XRPD is a powerful tool for material characterization in general, and for in-situ studies of chemical processes in particular. The use of an intense X-ray source, .i.e. synchrotron X-rays, coupled with fast X-ray detection permits time-resolved diffraction experiments allowing in-situ quantitative phase analysis during the early ages of cement hydration. Calcium sulfoaluminate, CSA, cements may have variable compositions, but all of them contain high amounts of ye'elimite, Ca4Al6O12SO4. Commercial CSA cements have special applications such as high strength developments at early-ages. Ye'elimite is very reactive and most of its hydration heat is released during the first eight hours of hydration . The aim of this work is to better understand the early age hydration of stoichiometric (orthorhombic) and doped (pseudo-cubic) ye'elimite samples. The parameters studied by SXRPD, LXRPD and calorimetry have been: polymorphism; water/ye'elimite ratio; and sulfate (gypsum and anhydrite) contents. This work has allowed establishing mechanisms and kinetics for hydration of ye'elimite samples by in-situ SXRPD with internal standard methodology. Moreover, pastes were also studied by ex-situ LXRPD with the external standard method, G-factor, at 2 and 7 days. Both strategies were able to quantify the amorphous contents, including free water. It is important to highlight that the results obtained at early ages, by the internal standard method, are in agreement with those obtained at later ages, G-method, showing the consistence and complementarity of both methodologies. The hydration of stoichiometric ye'elimite in the presence of gypsum is strongly hastened, when compared to the hydration process without gypsum. However, the presence of gypsum has a little effect in the hydration of doped ye'elimite. Moreover, anhydrite has also accelerated the hydration of stoichiometric ye'elimite, although its lower solubility has provoked the formation of an intermediate phase in the first hours.
Crystallochemical aspects of two microlite-group new mineral species
Authors: Andrade Marcelo , Ellena Javier , Atencio Daniel
Published: November 2015

Fluorcalciomicrolite, Ca1.5Ta2O6F, and hydroxycalciomicrolite, Ca1.5Ta2O6(OH), are new microlite-group [1] minerals found in the Volta Grande pegmatite, Nazareno, Minas Gerais, Brazil. Both occur as octahedral and rhombododecahedral crystals. The crystals are colourless, yellow and translucent, with vitreous to resinous luster. The densities calculated for fluorcalciomicrolite [2] and hydroxycalciomicrolite are 6.160 and 6.176 g/cm3, respectively. The empirical formulae obtained from electron microprobe analysis are (Ca1.07Na0.81□0.12)Σ2(Ta1.84Nb0.14Sn0.02)Σ2[O5.93(OH)0.07]Σ6.00[F0.79(OH)0.21] for fluorcalciomicrolite and (Ca1.48Na0.06Mn0.01)Σ1.55(Ta1.88Nb0.11Sn0.01)Σ2O6[(OH)0.76F0.20O0.04] for hydroxycalmicrolite. Fluorcalciomicrolite is cubic, space group Fd-3m, a = 10.4191(6) Å, V = 1131.07(11) Å3, and Z = 8. Hydroxycalciomicrolite is also cubic; however, the presence of P-lattice is confirmed by the large number of weak reflections observed by X-ray diffraction. As a result, the space group is P4332 and unit-cell parameters are a = 10.4211(8) Å, and V = 1131.72(15) Å3.
Crystal structure interconnections in a family of hydrated phosphate-sulfates
Authors: Yakubovich Olga , Steele Ian , Karimova Oxana
Published: November 2015

The phosphate-sulfate family incorporates several water-containing hypergene minerals with various structures. We determined the crystal structure of lately discovered [1] fibrous mineral arangasite, [Al2F(H2O)6(PO4)(SO4)]·3(H2O) using single-crystal synchrotron diffraction at 100 K (a =7.073(1), b=9.634(2), c=10.827(2) Å, β=79.60(1)0, P2/a, Z=2). Its crystal chemical interpretation has allowed us to reveal some interesting features in a title group of compounds. The arangasite crystal structure is dominated by chains extending in the [100] direction and built of pairs of corner-shared Al octahedra joined through bridging F atoms and P tetrahedra. They alternate in the [001] with S tetrahedra forming layers parallel to the ac plane through a system of hydrogen bonds. Along [010] the complex layers are separated by layers of H2O molecules. Hydrogen bonding serves here as the only mechanism providing linkage between the main structural fragments. The Al/ P chains are topologically identical to the chains built from Fe octahedra and P tetrahedra in the triclinic structure of destinezite, Fe2(OH)(PO4)(SO4)(H2O)6[2]. The repeating subunit of both chains consists of two octahedra and one tetrahedron sharing vertices. A main difference among the chains arises from their chemistry; Al octahedra in arangasite form pairs by sharing the F vertex of neighboring polyhedra, whereas pairs of Fe octahedra in destinezite are linked together through the oxygen vertex of an OH group. As a result, the larger size of the Fe octahedra compared to Al octahedra causes a larger c = 7.31 Å along the chain in destinezite. Additional SO4tetrahedra here are attached to these chains along their periphery through an oxygen vertex bridge with Fe octahedra. The monoclinic sanjuanite, Al2(PO4)(SO4)(OH)(H2O)9structure [3] is composed of Al/P chains, parallel to a = 6.11 Å. These chains are also built from three-member units that include corner-sharing pairs of octahedra connected by PO4tetrahedron, but they are not topologically equivalent to the chains in the arangasite and destinezite structures. Similar to arangasite, sulfate groups and H2O molecules reside between chains in the sanjuanite structure with hydrogen bonding. Thus, similar the crystal chemical formulae of sanjuanite and arangasite differ with respect to the (OH) → F substitution, which results in contrasting unit cell parameters. Note, that the unit cell volume of sanjuanite, is twice as large as arangasite.
Fitting the Pieces of the Puzzle: The Delta Bond
Authors: Murillo Carlos
Published: November 2015

The first compound with a quadruple bond was described by Al Cotton et al on August of 1964 (Cotton, F. A.; Curtis, N. F.; Harris, C. B.; Johnson, B. F. G.; Lippard, S. J.; Mague, J. T.; Robinson, W. R.; Wood, J. S. Science 1964, 145, 1305.). Since that time X-ray crystallography along other techniques such as EPR, electrochemistry, NMR, PES, electronic spectra, circular dichroism, magnetism, theoretical calculation have played an important role understanding of the delta bond. Here we will discuss some of the latest advances in the field.
Purely organic magnets: How to get ferromagnetic interactions
Authors: Campo Javier , Luzon Javier , Cañadillas Laura , Amaya Naoki , Palacio Fernando , Hosokoshi Yuko
Published: November 2015

Purely organic magnets, materials with spontaneous magnetization despite no containing magnetic ions, are very promising for technological applications due to their peculiar properties as flexibility, lightness or even biocompatibility. Most of the published purely organic magnets are free radical compounds. One of the most important difficulties in order to get spontaneous magnetization in such materials is that magnetic interactions among free radicals are usually antiferromagnetic and, in addition, ferromagnetic interactions are weaker than the antiferromagnetic ones. A possible strategy to overcome this issue is the use of triradical molecules with total spin S=1/2. In this case, an adequate packing of the triradical molecules can give place to antiferromagnetic interactions between regions with positive spin density and regions with negative spin density of two close molecules. This antiferromagnetic interaction between regions with opposite spin density would result in an overall ferromagnetic interaction between the two close triradicals. With this idea in mind we have performed an study of the spin density distribution and of the intramolecular and intermolecular magnetic interactions of the triradical compound 2-[3',5'-bis(Ntert-butylaminoxyl)phenyl]-4,4,5,5-tetramethyl-4,5-dihydro-1-Himidazol-1-oxyl-3-oxide, containing two N-tert-butyl aminoxyls and a nitronyl nitroxide groups. Combination of experimental data from a polarized neutron diffraction experiment and ab initio calculations (DFT) has allowed us to obtain the spin density distribution. In addition, the intramolecular and intermolecular magnetic interactions have been computed by ab initio quantum chemistry methods. The values for the intramolecular interactions confirm the S=1/2 ground state of the triradical. As for the intermolecular interactions, the two strongest ones are ferromagnetic, what is in agreement with the overlapping of regions with opposite spin density of the two interacting triradicals. These results support the strategy of using triradical molecules for obtaining purely organic magnets with higher magnetic transition ordering temperatures since is easier to obtain ferromagnetic interactions between the radicals and these interactions, having an antiferromagnetic origin, can be stronger than typical ferromagnetic interactions between radicals.
An unique model for joint refinement of (polarised) neutron and X-ray data
Authors: Claiser Nicolas , Deutsch Maxime , Gillon Béatrice , Gillet Jean-Michel , Lecomte Claude , Luneau Dominique , Souhassou Mohamed
Published: November 2015

A new charge and spin density model and the corresponding refinement software were recently developed to combine X-ray and polarised neutron diffraction experiments [1,2]. This joint refinement procedure allows for an access to both the charge and spin densities but also to spin up ( ) and spin down ( ) electron distributions. These two quantities ( and ) were thus separately modelled and for the first time it was possible to compare them with theoretical results. The first part of the presentation will introduce the refinement procedure and describe its application to the case of an end-to-end azido double bridged copper(II) complex[3]. The results of this joint refinement of X-ray and polarized neutron diffraction data will be compared to theoretical calculations. The second part will be devoted to recent applications to other materials including a purely organic radical.
Phase Identification by Rotation Electron Diffraction from Multiphasic Samples
Authors: Yun Yifeng , Wan Wei , Rabbani Faiz , Su Jie , Hovmöller Sven , Johnsson Mats , Zou Xiaodong
Published: November 2015

Electron Crystallography is an important technique for studying micro- and nano-sized crystals[1]. Crystals considered as powder by X-ray diffraction behave as single crystals by electron diffraction. Recently we developed a new method, Rotation Electron Diffraction (RED) for three-dimensional diffraction data collection by combining electron beam tilt with goniometer tilt on a transmission electron microscope (TEM)[2]. Here we apply the RED method on an unknown oxide sample in a Ni-Se-Cl-O system, which may show special physical properties, for example magnetic properties. The crystals in the sample were less than a few micrometers in sizes. Powder X-ray diffraction patterns of the sample could not be indexed by existing known phases. The sample was thus studied by TEM. Five 3D RED datasets were collected from five crystals with different morphologies using the software package RED. The data processing was also performed using the software RED-processing. The unit cell and space groups of all the five phases were obtained using RED and the structures of four of five phases were solved. Nearly all peaks in the powder X-ray diffraction pattern could be indexed using these five phases. To conclude, five phases from a powder sample have been identified using RED. RED is a powerful method for phase identification of multiphasic samples with nano-sized crystals.
Modeling X-ray diffractomerers using ray tracing and parallel coprocessors
Authors: Bokhimi Xim , Gonzalez Carlos
Published: November 2015

In X-ray powder diffraction, the use of the Rietveld technique to refine crystalline structures requires modeling the diffractometer. Some of the codes using this technique incorporate simple models for it. These codes do not affect the refined parameters only when the X-ray source is a synchrotron with enough X-ray optic to reduce the associated aberrations. When the diffractometer belongs to a standard laboratory, however, the optic associated to it gives rise to large aberrations; for example, asymmetric and shifted peaks that depend on the diffraction angle. When the above codes are used to refine crystalline structures, the refined parameters are non-confident, because they are partially modeling these aberrations. If in the code, the effect of the optical components on the diffraction pattern is modeled correctly, the obtained refined parameters will be more confident. This kind of modeling has been done in the codes that use the fundamental parameters model for the diffractometer. There are two ways to perform this modeling: in one of them the codes use an analytical model for each one of the optical components of the diffractometer; other codes use the ray tracing technique to model the path of the x-rays along the optic. This last technique requires a powerful computer facility. In this work, we present the developing of an open-source code to model the diffractometer by using the ray tracing technique. To reduce the calculation time, the code was written in OpenCL for a computer with a Fermi K20 coprocessor, and for a computer with a Xeon-Phi coprocessor, using the Qt platform for both systems. The device-function generated with this code can be used as input for any other code that models diffraction patterns, or refines crystalline structures. The code can also be used for teaching the effect of the different optical components on an X-ray powder diffraction pattern, including the effect of a wrong alignment of these components.
Crystallization Behaviors of Linear Polymers in Spin-coating Processes Traced by GISWAXS Measurements
Authors: Sasaki Sono , Hata Ryosuke , Tsuji Yuki , Hoshiba Jiro , Sakurai Shinichi , Hikima Takaaki , Masunaga Hiroyasu , Tashiro Kohji , Takata Masaki
Published: November 2015

The purpose of this study is clarification of crystallization behaviors of linear polymers in spin-coating film-forming processes on the molecular scale by time-resolved measurements of grazing-incidence small-angle and wide-angle X-ray scattering (GISAXS and GIWAXS: GISWAXS) measurements using synchrotron radiation. A sample used in this study was a commercially-available poly(3-hydroxybutyrate) (P3HB) (Sigma-Aldrich, Mw=437,000, Mw/Mn=1.67, Tg= 276 K) which was a biobased and biocompatible polyester. By spin-coating at rotational speeds of 1000 – 4000 rpm with using 0.49, 1.0, and 2.1wt% chloroform solutions of the P3HB, P3HB thin films with thicknesses of ca. 30 –600 nm were formed on silicon substrates. In these spin-coating processes at 296K, GISAXS and GIWAXS patterns from the sample on the substrate were simultaneously detected at BL45XU of SPring-8 (Hyogo, Japan). At the beginning of spin-coating, an isotropic scattering pattern from the solution was observed. Next, anisotropic Bragg reflections from oriented orthorhombic crystals of P3HB appeared and increased in intensity for several tens seconds. This indicated that P3HB chains crystallized as chloroform evaporated from the sample. It was also found that P3HB orthorhombic crystal having edge-on orientation was preferentially formed in thinner films. When the rotational speed of the substrate increased, the apparent induction period of crystallization slightly increased and the crystal growth rate decreased. This implied that the chain mobility of P3HB for crystallization might reduce due to a reduction in quantity of the solvent molecules and an increase in magnitude of the centrifugal force. These results obtained in this research would be important knowledge to improve film processing technologies for biobased polymeric materials.
Exploring fibrous materials with micro/nanobeam scanning diffraction techniques
Authors: Dane Thomas , Di Cola Emanuela , Lardiere Lionel , Montero Cedric , Sztucki Michael , Weinhausen Britta , Burghammer Manfred
Published: November 2015

Fibrous materials play an important role in many fields of research spanning from industrial applications to life sciences. They are typically organized in hierarchical arrangements of structural features on multiple length scales. Employing focused monochromatic x-rays combined with scanning diffraction, such samples can be studied obtaining rich information in reciprocal space (molecular to mesoscale level) and direct space simultaneously [1][2]. The resolution of the latter is mainly limited by the focal spot size ranging from a few microns down to 100 nm and less. The arrival of fast, sensitive pixel array detectors during the past years and the availability of high performance focusing optics enable in-situ studies on weakly scattering specimen like single polymer fibers and bio-composite materials (e.g. wood, bone tissue, ...) controlling environmental parameters such as humidity, temperature, and mechanical deformation. In this contribution we will present in a first part the state of the art of instrumentation for such experiments at the ESRF Microfocus Beamline, illustrated with recent examples. The figure below shows an example of a single fiber diffraction pattern of a high performance polymer (KEVLAR®) obtained from a 20 ms exposure with a 1.5 micron beam (Frelon CCD detector, 2k x 2k pixels, 13 keV photon energy). In the second part, future opportunities for scanning diffraction experiments emerging from potential upgrades of 3rd generation synchrotron radiation sources, as currently explored at the ESRF and elsewhere, will be discussed.