Atomistic modeling of the ( a + c ) -mixed dislocation core in wurtzite GaN

An atomistic simulation of the threading (a+c) -mixed dislocation core in wurtzite GaN has been carried out. Starting from models generated in the framework of continuum elasticity theory, two core configurations are obtained independently by using an empirical potential and a tight-binding based ab initio method. The most energetically favorable core with a 5/7 -atoms ring structure is fully coordinated without wrong bonds, whereas the other with a complex double 5/6 -atoms ring structure contains two rows of dangling bonds. Both core configurations introduce empty states spread over the upper half of the band gap.