Xcy. Lee et X. Gonze, THE PRESSURE-INDUCED FERROELASTIC PHASE-TRANSITION OF SIO2 STISHOVITE, Journal of physics. Condensed matter, 7(19), 1995, pp. 3693-3698
Using a newly developed accurate ab initio technique, we study the sta
bility and the lattice dynamics of SiO2 polymorph stishovite as a func
tion of pressure. We observe a ferroelastic phase transition to CaCl2
structure at 64 GPa, driven by a mechanical instability associated wit
h a vanishing shear modulus. Other lattice instabilities due to phonon
anomalies are theoretically excluded along with a proposed softening
of the B1g phonon mode.