Raman spectroscopic study of the selenite minerals—chalcomenite CuSeO₃·2H₂O, clinochalcomenite and cobaltomenite

Abstract

Raman spectroscopy has been used to study the dimorphous selenite minerals chalcomenite, cobaltomenite and clinochalcomenite. Selenite minerals are characterised by the position of the symmetric stretching mode which is observed at higher wavenumbers than the antisymmetric stretching mode. The selenite ion has C 3v symmetry and four modes, 2A 1 and 2E. These modes are observed at 813, 472 cm -1 (A 1 ) and 685, 710, 727 and 367 and 396 cm -1 (E). Bands assigned to the water stretching vibrations are observed for chalcomenite at 2953, 3184 and 3506 cm -1 and for clinochalcomenite at 2909, 3193 and 3507 cm -1 . A comparison of the Raman spectra of chalcomenite, clinochalcomenite and cobaltomenite is made. The position of these bands enabled hydrogen bond distances in the selenite structure to be estimated. Hydrogen bond distances for chalcomenite and clinochalmenite were determined to be similar.

A High-pressure Investigation of the Synthetic Analogue of Chalcomenite, CuSeO₃∙2H₂O

“…At low pressure we have observed twenty-two modes. They agree well with previous reported frequencies from different samples [7]. They also agree with our calculated frequencies, which are also in agreement with infrared experiments [44,45].…”

“…The low-frequency modes can be assigned to internal vibrations of the SeO3 and CuO5 polyhedra. The high-frequency modes correspond to water vibrations [7]. Our calculations confirm this interpretation.…”

“…The rest 129 modes are Raman active, with the B modes being also infrared active. Out of these modes, a total of twenty-one Raman modes have been measured in different samples of synthetic and natural chalcomenite [7] for frequencies smaller than 1000 cm -1 . In addition, three broad bands have been measured above 2900 cm -1 [7].…”

“…Out of these modes, a total of twenty-one Raman modes have been measured in different samples of synthetic and natural chalcomenite [7] for frequencies smaller than 1000 cm -1 . In addition, three broad bands have been measured above 2900 cm -1 [7]. The low-frequency modes can be assigned to internal vibrations of the SeO3 and CuO5 polyhedra.…”

“…An empty cavity occurs in the structure which is related to the Se lone pair of electrons. After the accurate determination of the crystal structure, most studies of chalcomenite have been focused in its lattice vibrations [6,7] and thermophysical and thermochemical properties [8,9]. All these studies have been carried out at ambient pressure.…”