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Free keywords:
mixed-valence arsenic; high pressure synthesis; powder diffraction structure analysis; X-ray diffraction; synchrotron radiation
Abstract:
We report on a new mixed valence arsenic(III,V)oxoacid H6As73+As75+O31 which crystallizes in the hexagonal space group P6(3) (no. 173), with lattice parameters a = 12.0525(1) angstrom, c = 4.7344(l) angstrom, v = 595.6(1) angstrom(3) and Z = 2. This phase is metastable and upon heating the RT-phase of As2O5 is recovered. The structure exhibits the first As5+ atom with a fivefold coordination by oxygen atoms in the shape of a distorted square pyramid. The positions of the hydrogen atoms were determined during the structure refinement from high resolution synchrotron powder diffraction data by difference Fourier analysis.
