Investigation of the order continuum in the evolution of quenched silicon using accelerated molecular dynamics techniques

The thermodynamic, electronic and structural properties of silicon phases are inextricably linked to the underlying order in the material. While the crystalline and amorphous phases are well characterized, the existence of a glassy silicon phase is unknown as the quench rate 'window' available to experiments is too low to observe this material, except perhaps transiently. Our interest lies in characterizing order in the various solid phases of Si, looking in particular at phases with partial order. In traditional Molecular Dynamics (MD) studies, the accessible timeframe is too small, and the underlying kinetics too sluggish, to be confident that the MD results represent complete equilibrium. We have implemented accelerated MD methods like Hyper-MD (HMD) and Self-Guided MD (SGMD) for a system of atoms interacting via a Stillinger-Weber (SW) potential to reduce the effects of frequent, but nonessential, events. We have used these approaches to study the evolution of glassy and amorphous silicon from the relaxation of an ultra-rapidly quenched liquid and investigated the inherent structural order and its relationship to key system properties.