Computational searches for crystal structures of dioxides of group 14 elements (CO 2 , SiO 2 , GeO 2 ) under ultrahigh pressure.

In this study, we focused on the effect of pressure on the crystal structures of dioxides of group 14 elements, i.e. SiO 2 , GeO 2 , and CO 2 . 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 SiO 2 , GeO 2 , and CO 2 , respectively, at 1 and 10 6 atm. At 1 atm, cristobalite-like, quartz, anatase-like, and stishovite were stable structures for SiO 2 and GeO 2 . At 10 6 atm, structures of stishovite and CaCl 2 type were relatively stable for SiO 2 and GeO 2 . At 1 atm of CO 2 , molecular crystals were the most stable, whereas, quartz-like and cristobalite-like structures were obtained as stable structures at 10 6 atm. We discuss these pressure dependent structural variations systematically using the obtained structural dataset.