Raman study of temperature dependence of lattice modes in calcite

Abstract

The temperature dependence of the line width and the peak position of the E_g librational mode (of nominal frequency 285 cm⁻¹) and the E_g translational mode (of nominal frequency 155 cm⁻¹) in calcite (CaCO₃) have been studied by laser-Raman spectrometry. The role of orientational relaxation as a possible process contributing to the line width has been evaluated. It is concluded that reorientations do not play a major part in relation to the present observations. It is further shown that the latter can be understood on the basis of cubic and quartic anharmonic processes. The data also suggest that certain phonon interactions earlier considered insignificant for peak shift in calcite, do contribute significantly.