Morse stretch potential charge equilibrium force field for ceramics: Application to the quartz-stishovite phase transition and to silica glass

To predict phase transitions in ceramics and minerals from molecular dynamics simulations, we have developed a force field in which the charges are allowed to readjust instantaneously to the atomic configurations. These charges are calculated using the charge equilibration (QEq) method. In addition to electrostatics, a two-body Morse stretch potential is included to account for short-range nonelectrostatic interactions. This MS-Q potential is applied herein to SiO₂where we find that it describes well the fourfold coordinated and sixfold coordinated systems (such as quartz and stishovite), silica glass, and the pressure-induced phase transition from quartz to stishovite.