High-density liquidlike component facilitates plastic flow in a model amorphous silicon system

Molecular dynamics simulations show that plastic deformation of amorphous Si modeled by the Stillinger-Weber potential is very sensitive to the density of the initial unstressed state. Low-density systems exhibit a pronounced yield phenomenon, strain softening, and a dramatic drop in pressure during deformation at a constant volume. This behavior is explained by the presence in every system of a certain concentration of solidlike and liquidlike components, the latter being denser and more amenable to plastic flow.