Structural units and low-energy configurations of [0001] tilt grain boundaries in GaN

The potential energy of [0001] tilt coincidence grain boundaries has been calculated using a Stillinger-Weber potential that was previously adapted to wurtzite (GaN) in order to take into account the Ga-Ga and N-N wrong bonds. The atomic structures of the grain boundaries have been determined for the lowest-energy configuration. They are described in terms of a limited number of structural units corresponding to the cores of the 1/3[11 (2) over bar0] edge dislocation. The potential energy curve versus tilt angle shows two energy minima for Sigma = 7 and 13.