Soft localized excitations in computer glasses

Glasses are solids in which the atoms vibrate about disordered points in space, as opposed to crystals in which the atoms vibrate about the points of a lattice.
In glasses there exist rare local environments that allow small groups of particles to vibrate at an unusually low energetic cost. We call these motions low-energy (or “soft”) localized excitations. These excitations are of fundamental importance in the statistical mechanics and dynamics of glasses, which are markedly different from their crystalline counterparts, yet display a striking degree of universality and are not well understood.
This thesis investigates soft localized excitations in glasses by computer simulation of simplified model systems. My contributions fall into three broad categories: (1) the study of the statistical and mechanical properties of soft localized excitations; (2) the development of new computational methods to reliably extract these excitations from computer glasses and more fully characterize and analyze them; (3) the application of these analyses to open problems in glass physics, such as the non-Arrhenius solidification, the history dependence of thermal and mechanical properties and the rate of elastic wave attenuation.