Ab initio structure determination from powder diffraction and Maximum entropy image reconstruction

Jae-Hyuk Her State University of New York at Stony Brook

Modern scientific understanding of materials starts from knowing their structures, where single crystal diffraction dominates. Many scientifically and/or practically interesting materials, however, often exist only in a polycrystalline (powder) form. Fortunately, recent developments based on high resolution powder diffraction data allow one to solve rather complicated crystal structures. In this talk, the structure solution of molecular magnet and hydrogen storage materials will be presented, which reveals unexpected features and provided natural explanations for previously observed experimental results. The second topic concerns a frequently met difficulty; how to treat the crystallographically poorly defined scattering densities which defy conventional atomic model approaches. The Maximum entropy method with a Pawley fit makes best use of information contained in the X-ray powder diffraction pattern by considering the correlation between partially overlapped reflections.

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