Computational searches for crystal structures of dioxides of group 14 elements (CO2, SiO2, GeO2) under ultrahigh pressure

Abstract

In this study, we focused on the effect of pressure on the crystal structures of dioxides of group 14 elements, i.e. SiO₂, GeO₂, and CO₂. Systematic searches for their crystal structures using the artificial force induced reaction method generated 219 and 147, 102 and 63, and 148 and 76 structures for SiO₂, GeO₂, and CO₂, respectively, at 1 and 10⁶ atm. At 1 atm, cristobalite-like, quartz, anatase-like, and stishovite were stable structures for SiO₂ and GeO₂. At 10⁶ atm, structures of stishovite and CaCl₂ type were relatively stable for SiO₂ and GeO₂. At 1 atm of CO₂, molecular crystals were the most stable, whereas, quartz-like and cristobalite-like structures were obtained as stable structures at 10⁶ atm. We discuss these pressure dependent structural variations systematically using the obtained structural dataset.