CRYSTAL-STRUCTURE OF A NEW HYDROGEN BISMUTH CHROMATE - HBI3(CRO4)(2)O-3

The new compound HBi3(CrO4)(2)O-3 has been prepared hydrothermally. The yellow needles crystallize in space group P2(1)/a with a = 5.527(7)Angstrom, b = 12.214(3)Angstrom, c = 14.003(3)Angstrom, beta = 92.95(2)degrees and Z = 4. A single crystal X-ray diffraction structure determination and refinement yields R = 4.1% and Rw = 4.8%. Chromium is present in two crystallographically distinct (CrO4)(2-) groups. Sheets formed from bismuth and oxygen are perpendicular to the c-axis. The chromate groups bridge the sheets. Valence bond calculations indicate that the hydrogens are also in the intersheet region and are shared between two crystallographically distinct oxygen atoms.