Damage inhomogeneity in the core region of displacement cascades in simplified nuclear glasses

Displacement cascades at energies ranging from 16 keV to 70 keV were simulated by classical molecular dynamics. Damage inhomogeneity was observed in each case: the atomic density was diminished by the incident projectile to a variable extent depending on the regions concerned. The regions near the initial projectile position are largely annealed, and regions near the end of the cascade are relatively unaffected because of the low residual projectile energy. However, maximum damage occurs in intermediate regions from collisions with incident projectiles at energies ranging from about 10 keV to 25 keV. This phenomenon illustrates the competition between structure annealing and projectile-induced damage: both increase with the local energy, but with different dynamics. At the highest energies, annealing wins out over damage, restoring the glass structure to its pristine state; hence the good structural behaviour in the zones closest to the initial projectile position, which are subjected to the greatest local temperature rise.