Dynamics of structural transitions in liquids

The "inherent structures" which underlie the liquid state are those stable particle packings (potential minima) which can be reached by a steepest-descent quench on the potential-energy hypersurface. This paper explores the dynamics of transition between distinct inherent structures for a simple classical model of monatomic substances. Molecular-dynamics calculations with 32 and 108 particles have been carried out with running construction of the mapping to potential minima. This determines the distribution of stable packings according to their potential energy and shows how transition rates between alternative structures vary with total system energy. Melting and freezing events have been monitored in this manner. We observe occasional transitions in localized "two-state" (bistable) systems in strongly supercooled amorphous states. Transitions in fluid states display a peculiar intermittency that may have relevance to self-diffusion and viscous flow.