- Molecular-dynamics simulation of amorphous silicon (a-Si) using the Stillinger-Weber potential reveals the existence of two distinct atomic environments: one solidlike and the other liquidlike. The mechanical behavior of a-Si when plastically deformed to large strain can be completely described by the mass fraction of liquidlike material in it. Specifically, samples with higher are more amenable to plastic flow, indicating that liquidlike atomic environments act as plasticity "carriers" in a-Si. When deformed under externally applied constant pressure, all a-Si samples converge to a unique value of characteristic of steady-state flow. 2005 The American Physical Society.