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Li2MnSiO4 has been identified recently as one of the first cathode battery materials that, at least in principle, could exchange more than 1 lithium per redox-active transition metal ion. In this article, we analyze experimentally and by computer simulations based on density functional theory (DFT) why actual experiments have not confirmed these expectations. We show that Li2MnSiO4 is unstable upon delithiation, with a strong tendency to amorphize. Detailed DFT calculations further indicate that it might be possible to obtain a stable material with a reversible exchange of more than one Li per formula unit (FU) by using an appropriate Mn/Fe mixture (solid solution) with a general formula Li2Mn x Fe1 - x SiO4.

Dedicated to Professor Hans Paulsen on the occasion of his 75th birthday (23.XII. 1996) The solid-state structures of three stereoisomers, 1-3, of the cyclic tetramer of 3-aminobutanoic acid are presented. These cyclo-p-peptides were found to be highly insoluble materials, and it proved to be impossible to grow crystals of suficient quality for X-ray single-crystal analysis. The samples of 1-3 were, however, suitable candidates for structure determination from powder diffraction data (Fig. Z), and the application of this method is described. All three isomers have been found to adopt tubular structures (Figs. 2-4) in a fashion similar to those already observed for certain cyclo-a-peptides. The stacks of 16-membered rings are held together by four nonlinear C=O ...H-N H-bonds between pairs of molecules (Fig. 5 ) .

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The triclinic form of AlPO 4 -34, a microporous aluminophosphate with the chabazite (CHA) topology, adopts a rhombohedral symmetry upon calcination. The framework structure of this phase remains intact under ambient conditions, but it distorts dramatically, though reversibly, in the presence of water. Following these structural changes in situ by X-ray diffraction revealed that there are actually two stable rehydrated phases, which differ from each other by one water molecule in the channel. Both of these phases have triclinic unit cells that are closely related to that of the calcined rhombohedral phase. The structure of the low-temperature (10 °C), fully rehydrated phase (phase B) was elucidated by combining high-resolution synchrotron powder diffraction with solid-state NMR techniques. Coordination of three of the six Al atoms to water molecules causes the deformation of the framework and the reduction of the symmetry. Rietveld refinement of the structure of phase B in the triclinic space group P1 (a ) 9.026, b ) 9.338, c ) 9.508 Å, R ) 95.1°, β ) 104.1°, and γ ) 96.6°) converged with R F ) 0.079 and R WP ) 0.176 (R exp ) 0.087). Framework connectivities derived from the structure were used to assign 31 P NMR lines as well as part of the 27 Al NMR signal.

We report on the properties of a new air-stable nanowire material with the chemical formula Mo6S3I6. The distinguishing features of the material are rapid one-step synthesis, easy isolation and controllable dispersion into small-diameter wire bundles. Elemental analysis, x-ray diffraction, thermogravimetry, differential thermal analysis, Raman scattering and electron microscopy were used to characterize the material.

Moybdenum-based subnanometre diameter nanowires are easy to synthesize and disperse, and they exhibit a variety of functional properties in which they are superior to other one-dimensional materials. However, further progress in the understanding of physical properties and the development of new and specific applications have so far been impeded by the fact that their structure was not accurately known. Here we report on a combination of systematic x-ray diffraction and extended x-ray absorption fine structure experiments, and first-principles theoretical structure calculations, which are used to determine the atomic skeletal structure of individual Mo6S9−xIx (MoSIx) nanowires, their packing arrangement within bundles and their electronic band structure. From this work we conclude that the variations in functional properties appear to arise from different stoichiometry, not skeletal structure. A supplementary data file is available from http://stacks.iop.org/0957-4484/16/1578

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