Autocatalytic avalanches of unit inelastic shearing events are the mechanism of plastic deformation in amorphous silicon

Discrete stress relaxations were found to be the source of low-temperature plastic flow in amorphous silicon (a-Si) as modeled by atomistic simulation using the Stillinger-Weber potential. These relaxations are triggered when a local yielding criterion is satisfied in a small cluster of atoms. The atomic rearrangements accompanying discrete stress relaxations are describable as autocatalytic avalanches of unit shearing events. Every such unit event centers on a clearly identifiable change in bond length between the two split peaks of the second nearest-neighbor shell in the radial distribution function of bulk a-Si in steady-state flow.