Atomic structural evolution of pressure-induced amorphization processes in beta-cristobalite

The changes in the atomic structure of beta-cristobalite before and after the onset of the amorphization are examined in detail by analysing the Molecular Dynamics trajectories of Si and O ions. it is found that long Si-O bonds with bond lengths of 1.9-2.5 Angstrom emerge after the onset of amorphization. Most of oxygen ions bonded to Si with long Si-O bonds come from neighbouring SiO4 tetrahedrals. The breakage of Si-O bonds is found to occur frequently during the amorphization process, with the majority of the broken bonds being long Si-O bonds. Our results show that bond breaking and relatively large atomic displacements play important roles in the pressure-induced amorphization of beta-cristobalite and that the structural changes in the material during amorphization involve both short and inter-medium range orders.