Dynamical simulations of nonequilibrium processes - Heat flow and the Kapitza resistance across grain boundaries

We report molecular dynamics simulations of nonequilibrium heat flow in a solid system in the local-equilibrium or hydrodynamic approximation and demonstrate that local equilibrium can be achieved in small numbers of atomic layers over long simulation runs. From the dynamical simulations, we calculate the thermal boundary (Kapitza) resistance that arises from heat flow across Si grain boundaries and compare with the traditional approach based on calculating the transmission and reflection of harmonic phonons at the grain boundary.