Abstract
The stability of CO2 phases at pressures up to 1600 GPa is confirmed using evolution methods for predicting crystal structures. Stable CO2 phases are as follows: $$I\bar {4}2d$$ (to 279 GPa), $$P{{4}_{2}}{\text{/}}nmc$$ (279–952 GPa), Pbcn (952–1018 GPa), and $$Pa\bar {3}$$ (above 1018 GPa). The equations of state for stable CO2 phases up to pressures of about 1600 GPa are calculated for the first time using ab initio methods and high-temperature calculations within the quasi-harmonic approximation. It is shown that high-pressure $$P{{4}_{2}}{\text{/}}nmc$$ , $$Pbcn$$ , and $$Pa\bar {3}$$ phases have rather high bulk moduli (290–415 GPa). Phases with sixfold coordination of carbon atoms (Pbcn and $$Pa\bar {3}$$ ) have higher coefficients of thermal expansion in comparison with the $$P{{4}_{2}}{\text{/}}nmc$$ phase.