Ab Initio Study of Elastic Properties of High-Pressure Polymorphs of CO2 Phases II and V

Abstract

Elastic properties of prototypical CO2 polymorphs under compression are essential to understanding the nature of their pressure-induced structural changes. Despite the fundamental importance in physical chemistry and condensed matter physics and geophysical implications for the nature of fluids in the Earth and planetary interiors, the elastic properties of these polymorphs are not fully understood because of intrinsic uncertainty and difficulties in experimental estimation of elasticity. Theoretical calculations of elastic properties of high-pressure CO2 polymorphs allow us to reveal the previously unknown details of elasticity of the diverse polymorphs under extreme compression. As a step toward getting insights into the deep carbon cycle, we carried out density-functional-theory calculations and investigated the elastic constants, bulk modulus, shear modulus, Poisson ratios and acoustic wave velocities of CO2 polymorphs: II (tetragonal, P42/mnm), β-cristobalite-like V (VCR, tetragonal, I42d) and tridy...