Static and dynamic properties of solid CO2 at various temperatures and pressures

A constant pressure Monte Carlo formalism, lattice dynamics, and classical perturbation theory are used to calculate the thermal expansion, pressure–volume relation at room temperature, the temperature dependence of the zone center libron frequencies, and the pressure dependence of the three vibron modes of vibration, in solid CO2 at pressures 0≤p≤16 GPa and temperatures 0≤T≤300 K. The agreement with experiment is good. At room temperature the observed Pa3 phase is predicted for P≤11 GPa, above which a transition occurs into an orthorhombic Cmca structure, with a volume change upon transition of ΔV=0.4 cm3 /mol. Calculated physical quantities in this phase are consistent with experiment.