Pressure-induced amorphization of β-cristobalite

Abstract

A constant-pressure molecular-dynamics (MD) study using a three-body potential is employed to study the pressure-induced structural change in \ensuremath{\beta}-cristobalite in the pressure range of 0--23 GPa. Our MD results demonstrate that \ensuremath{\beta}-cristobalite gradually transforms from a crystalline phase to an amorphous phase in the range 11--15 GPa, and abruptly changes to a sixfold-coordinated amorphous silicon structure at 13.5 GPa. Upon release of pressure, the material does not transform back into \ensuremath{\beta}-cristobalite but remains in the amorphous phase with a silicon coordination of nearly six. The behavior of the pressure amorphization of \ensuremath{\beta}-cristobalite is found to be similar to that of pressure amorphization of \ensuremath{\alpha}-quartz. This similarity implies that they may have a similar order-disorder transition mechanism.