Vibrational spectroscopic study of multianion mineral clinotyrolite Ca2Cu9[(As,S)O4]4(OH)10·10(H2O)

The molecular structure of the mixed anion mineral clinotyrolite Ca2Cu9[(As,S)O4]4(OH)10·10(H2O) has been determined by the combination of Raman and infrared spectroscopy. Characteristic bands associated with arsenate, sulphate and hydroxyl units are identified. Broad bands in the OH stretching region are observed and are resolved into component bands. Estimates of hydrogen bond distances were made using a Libowitzky function and both short and long hydrogen bonds are identified.Two intense Raman bands at 842 and ∼796 cm−1 are assigned to the ν1 (AsO4)3− symmetric stretching and ν3 (AsO4)3− antisymmetric stretching modes. The comparatively sharp Raman band at 980 cm−1 is assigned to the ν1 (SO4)2− symmetric stretching mode and a broad Raman spectral profile centred upon 1100 cm−1 is attributed to the ν3 (SO4)2− antisymmetric stretching mode.

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► We have studied the molecular structure of the multianion mineral clinotyrolite Ca2Cu9[(As,S)O4]4(OH)10·10(H2O).
► We used a combination of Raman and infrared spectroscopy.
► The ratio of As:S is not 1:1.
► Characteristic bands associated with arsenate, sulphate, hydroxyl units are identified.