Simulation methods

Molecular dynamics simulations were carried out in a cubic box containing 3456 BKS (28–30) SiO₂ (3456 silicon and 6912 oxygen atoms) by using the LAMMPS (31) package. Periodic boundary conditions were applied in all directions. Intermolecular interactions were truncated at 5.5 Å, and long-range Coulomb interactions were treated by a particle-particle particle-mesh method. All simulations were performed in the constant-temperature, constant-pressure (NPT) ensemble. The temperature and pressure were kept constant by using the Nosé-Hoover thermostat and barostat, respectively. A time step of 1 fs was used in all the simulations below 6000 K. Above 6000 K, the time step was adjusted to 0.5 fs to avoid overlap of atoms within one step. More simulation details can be found in (25).