Identification of relaxation and diffusion mechanisms in amorphous silicon

The dynamics of amorphous silicon at low temperatures can be characterized by a sequence of discrete activated events, through which the topological network is locally reorganized. Using the activation-relaxation technique, we create more than 8000 events, providing an extensive database of relaxation and diffusion mechanisms. The generic properties of these events-size, number of atoms involved, activation energy, etc.-are discussed and found to be compatible with experimental data. We introduce a topological classification of events and apply it to study those events involving only fourfold coordinated atoms. For these, we identify and present in detail three dominant mechanisms.