Direct Calculation of Light-Induced Structural Change and Diffusive Motion in GlassyAs2Se3

Photostructural change of glassy ${\mathrm{As}}_2{\mathrm{Se}}_3$ was simulated on an experimentally credible model with excited electronic dynamics within first-principles molecular dynamics. Bond breaking and bond switching reactions account for local changes around defect sites at the short time phase of illumination. For long-time relaxation, defect pairs associated with band tail states become involved in a rearrangement in the network, giving rise to a low energy, nonlocal “polaronlike” collective oscillation. Diffusive motion is observed for short times, which we tentatively interpret as the initial phase of athermal photomelting.