The crystal structure of Hg0.75Mo0.25Sr2Cu4.5+delta, with delta = 0.10(1), has been determined from Rietveld analysis of neutron powder diffraction data. This material crystallises in space group P4/mmm with a = 3.7794(1) and c = 8.8600(3) Angstrom. The Mo cation in Hg0.75Mo0.25Sr2CuO4.5+delta is hexavalent and is co-ordinated to four oxygen anions, forming MoO42- oxyanions of near ideal tetrahedral symmetry. The partial replacement of linear HgO22- units by MoO42- tetrahedra is found to result in significant distortions of the neighbouring CuO6 and SrO8+delta polyhedra. Doping 4 of the CuO2 sheets in Hg0.75Mo0.25Sr2CuO4.5+delta is achieved by the intercalation of interstitial oxygen, with T, = 54 K for 6 = 0.10. (C) 2003 Elsevier B.V. All rights reserved.
- neutron diffraction
- crystal structure