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 Ca(2)Cu(9)[(As,S)O(4)](4)(OH)(10)·10(H(2)O) 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 ν(1) (AsO(4))(3-) symmetric stretching and ν(3) (AsO(4))(3-) antisymmetric stretching modes. The comparatively sharp Raman band at 980 cm(-1) is assigned to the ν(1) (SO(4))(2-) symmetric stretching mode and a broad Raman spectral profile centred upon 1100 cm(-1) is attributed to the ν(3) (SO(4))(2-) antisymmetric stretching mode.