Prediction of a hexagonal SiO2 phase affecting stabilities of MgSiO3 and CaSiO3 at multimegabar pressures.

ABSTRACT: Ultrahigh-pressure phase relationship of SiO(2) silica in multimegabar pressure condition is still quite unclear. Here, we report a theoretical prediction on a previously uncharacterized stable structure of silica with an unexpected hexagonal Fe(2)P-type form. This phase, more stable than the cotunnite-type structure, a previously postulated postpyrite phase, was discovered to stabilize at 640 GPa through a careful structure search by means of ab initio density functional computations over various structure models. This is the first evidential result of the pressure-induced phase transition to the Fe(2)P-type structure among all dioxide compounds. The crystal structure consists of closely packed, fairly regular SiO(9) tricapped trigonal prisms with a significantly compact lattice. Addition

SUBMITTER: Tsuchiya T 

PROVIDER: S-EPMC3029757 | biostudies-literature | 2011 Jan

REPOSITORIES: biostudies-literature