Large-scale molecular-dynamics simulations on heterogeneous state during decompression-induced transformation of short-range order in silica glass

Large-scale molecular-dynamics simulations with machine-learning interatomic potentials have shown that a nanometer-scale heterogeneous intermediate state emerges during the structural transformation of silica glass from a sixfold-coordinated state to a fourfold-coordinated state under decompression. The simulation results reproduce key experimental observations, including density changes and low-Q scattering intensity during decompression. The heterogeneity is explained by the distribution of the coordination number for silicon. The transformation proceeds via a relatively unstable fivefold-coordinated state, and its generation is followed by the formation of a fourfold-coordinated component that increases in proportion to the logarithm of time.