First Principles Simulation of Grain Boundary Sliding

We present the results of a total-energy pseudopotential simulation of the sliding process at a $\Sigma =5\mathrm{}$ (001) twist grain boundary in germanium. Sliding involves a stick-slip mechanism with local rebonding among a few atoms, accompanied by the clearance of gap states. At large strain, spreading of disorder from the boundary interface produces a loss of strength in the system and would induce fracture. Finally we investigate the effects of temperature and strain rate on the sliding behavior.