Tetrahedral ↔ octahedral network structure transition in simulated vitreous SiO2

By using molecular dynamics (MD) simulations we found a transition from a tetrahedral to an octahedral network structure in an amorphous SiO2 model under compression from 2.20 to 5.35 g/cm3. And on heating of a high density amorphous (hda) model of 5.35 g/cm3 at zero pressure, the structure transforms to a low density amorphous (lda) form. Simulations were done in a model containing 3000 particles under periodic boundary conditions with interatomic potentials which have a weak Coulomb interaction and a Morse type short-range interaction.