Raman spectroscopic study of the schmiederite Pb2Cu2[(OH)4|SeO3|SeO4]

Raman spectroscopy lends itself to the studies of selenites, selenates, tellurites and tellurates as well as related minerals. The mineral schmiederite Pb2Cu2[(OH)(4)vertical bar SeO3 vertical bar SeO4], is interesting, in that, both selenite and selenate anions occur in the structure. Raman bands of schmiederite at 1095 and 934 cm(-1) are assigned to the symmetric and antisymmetric mode of the (SeO4)(2-) anions. For selenites, the symmetric stretching mode occurs at a higher position than the antisymmetric stretching mode, as is evidenced in the Raman spectrum of schmiederite. The band at 834 cm(-1) is assigned to the symmetric (SeO3)(2-) units. The two bands at 764 and 739 cm(-1) are attributed to the antisymmetric (SeO3)(2-) units. An intense, sharp band at 398 cm(-1) is assigned to the v(2) bending mode. The two bands at 1576 and 1604 cm(-1) are assigned to the deformation modes of the OH units. The observation of multiple OH bands supports the concept of a much distorted structure. This is based upon the four OH units coordinating the copper in a square planar structure. A single symmetric Raman band is observed at 3428 cm(-1) and is assigned to the symmetric stretching mode of the OH units. The observation of multiple infrared OH stretching bands supports the concept of non-equivalent OH units in the schmiederite structure. Copyright (C) 2008 John Wiley & Sons, Ltd.