Infrared study of phase transition in solid CO2 under pressure

Abstract

Infrared spectra of solid CO2 were measured up to 20 GPa at ambient temperature. The transition from the cubic Pa3 phase to a high‐pressure phase was clearly detected at 12 GPa as discreet changes in the vibron frequencies. Pressure dependence of the vibron frequencies measured for the high‐pressure phase up to 20 GPa was not in agreement with those calculated previously for the presumed high‐pressure phase with an orthorhombic Cmca structure, suggesting the possibility that the high‐pressure phase has another crystal structure.