Authors: D.D. Klug, R. Rousseau, K. Uehara, M. Bernasconi and J.S. Tse
Affilation: National Research Council of Canada, Canada
Pages: 129 - 132
Keywords: high-pressure, ab initio calculations, Car-Parrinello, SiO2
The mechanism for the pressure induced transformation of cristobalite to stishovite and post-stishovite phases has been obtained from constant pressure ab initio molecular dynamics simulations. The cristobalite to stishovite transformation is found to be a two step process where SiO4 tetrahedra first rotate followed by a lattice distortion to yield the 6-coordinated stishovite structure. Further compression of stishovite yields the CaCl2 structure and is followed by another 6-coordinated structure with symmetry P21/n (at 11 Mbar) which remains stable to a pressure of about 14 Mbar and then transforms into a 9-coordinated P21/m structure.