The Crystal Structure of Szenicsite, Cu3MoO4(OH)4

Peter C. Burns
Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, Indiana 46556-0767, USA

Abstract: The crystal structure of szenicsite, Cu3MoO4(OH)4, orthorhombic, a = 8.5201(8), b = 12.545(1), c = 6.0794(6) Å, V = 649.8(2) Å3, space group Pnnm, Z = 4, has been solved by direct methods and refined by least-squares techniques to an agreement index (R) of 3.34% and a goodness-of-fit (S) of 1.11 for 686 unique observed [|4| ⩾ 4σF] reflections collected using graphite-monochromated Mo-Kα Xradiation and a CCD area detector. The structure contains three unique Cu2+ positions that are each coordinated by six anions in distorted octahedral arrangements; the distortions of the octahedra are due to the Jahn-Teller effect associated with a d9 metal in an octahedral ligand-field. The single unique Mo6+ position is tetrahedrally coordinated by four O2− anions. The Cu2+B6 (Ф: unspecified ligand) octahedra share trans edges to form rutile-like chains, three of which join by the sharing of octahedral edges to form triple chains that are parallel to [001]. The MoO4 tetrahedra are linked to either side of the triple chain of Cu2+Ф6 octahedra by the sharing of two vertices per tetrahedron, and the resulting chains are cross-linked through tetrahedral-octahedral vertex sharing to form a framework structure. The structure of szenicsite is closely related to that of antlerite, Cu3SO4(OH)4, which contains similar triple chains of edge-sharing Cu2+Ф6 octahedra.

Keywords: szenicsite • copper oxysalt • crystal structure • molybdate • Chile

Mineralogical Magazine; August 1998 v. 62; no. 4; p. 461-469; DOI: 10.1180/002646198547837
© 1998, The Mineralogical Society
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