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On the symmetry of wulfenite (Pb[MoO 4 ]) from Mežica (Slovenia)

2011; Wiley; Volume: 67; Issue: 6 Linguagem: Inglês

10.1107/s0108270111015769

1600-5759

Ildikó Cora, Mátyás Czugler, István Dódony, Aleksander Rečnik,

Solid-state spectroscopy and crystallography

Wulfenite [lead(II) molybdate(VI)] is known as a scheelite structure in the I4(1)/a space group. The structure of the unusual `hemimorphic' wulfenite crystals from the Meǽica mine was refined in the noncentrosymmetric space group I ̅4 using a Pb/Mo exchange disorder model with the approximate composition Pb(0.94)Mo(0.06)[MoO(4)]. Pb atoms in the 2b positions are substituted by Mo at about 12%. The crystal is shown to be twinned by inversion. Hemimorphism may result from the short-range chemical ordering of the metal atoms at the 2b positions.