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Frank Stowasser, Christof Renkenberger

Ab initio crystal structure determination of Bi₆Rh₁₂O₂₉ from powder diffraction data

Keywords: Simulated annealing, Todorokite-related structure, Ab initio structure analysis, X-ray powder diffraction, Bismuth rhodium oxide

The complex crystal structure of Bi₆Rh₁₂O₂₉ was determined from laboratory X-ray powder diffraction data with the software package TOPAS® [1]. The crystal symmetry is monoclinic (space group C2/m, Z = 4) and the unit cell parameters are a = 19.8510(1) Å, b = 12.24424(6) Å, c = 9.52367(5) Å and β = 97.2890(4)°. The structure is stable at normal pressure and room temperature. There are 4 Bi, 9 Rh and 18 O in the asymmetric unit and totally 188 atoms in the complete unit cell. Rhodium is coordinated by oxygen in slightly distorted edge sharing octahedra which build up crossing sheets both parallel (100) with a distance of d₁₀₀/2 and parallel (001) with a distance of d₀₀₁. The remaining channels along b contain the bismuth ions in irregular 6- and 8-fold coordination. Because of a small excess of oxygen in the formula – with respect to an expected amount of oxygen indicated by trivalent Bi and also trivalent Rh — the oxidation state of rhodium adjusts to a formal +3.33.

Zeitschrift für Kristallographie, Oldenbourg Wissenschaftsverlag

Print ISSN: 0044-2968
Volume: 221, 03/2006
Pages: 206 - 212

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