Atomistic Analogue of Coarse-Grained Glass Formers

Despite the remarkable success of coarse-grained glass formers in describing supercooled liquid behavior, two important pieces of the puzzle remain unsolved. First, the fundamental nature of the elementary excitations that are central to the theory remains unknown. Second, it is not known how these excitations, which represent a minimal element of dynamical heterogeneity, relate to the heterogeneous dynamics extensively characterized for atomistic, molecular, colloidal and granular systems. Here, for several atomistic models of glass formers, we use importance sampling of trajectory space to study the structure, statistics and dynamics of elementary excitations, all of which we relate to dynamic heterogeneity. We relate the excitations to bulk transport properties of the system, and show how the superposition of excitations in time gives rise to the unique dynamical patterns, such as strings and mobile clusters of strings, typically observed for glass forming liquids.