Influence of temperature and anisotropic pressure on the phase transitions in alpha-cristobalite.

The role of temperature and anisotropy of the applied load in the pressure-induced transformations of alpha-cristobalite is investigated by means of first principles molecular dynamics combined with the metadynamics algorithm for the study of solid-solid phase transitions. We reproduce the transition to alpha-PbO2 as found in experiments and we observe that the transition paths are qualitatively different and yield different products when a nonhydrostatic load is applied, giving rise to a new class of metastable structures with mixed tetrahedral and octahedral coordination.