  An intrinsic feature of nearly all internal interfaces in crystalline systems
(homo- and hetero-phase) is the presence of disconnections (topological line
defects constrained to the interface that have both step and dislocation
character). Disconnections play a major role in determining interface
thermodynamics and kinetics. We demonstrate that elastic interactions between
disconnections lead to a thermodynamic, first-order, finite-temperature,
faceting-defaceting transition, in agreement with experiments. These elastic
interactions strongly modify equilibrium interface morphologies (compared with
those solely determined by anisotropic surface energy) as well as the kinetics
and morphologies of migrating interfaces. We demonstrate these phenomena
through numerical simulations based upon a general, continuum
disconnection-based model for interface thermodynamics and kinetics applied to
embedded particles/grains, steady-state interface migration geometries, and
nominally flat interfaces.
