Ab Initio Modelling of Defects in Non-Metallic Systems

The simplicity of density functional methods and the increasing availability of computer-processing power have enabled ab initio modelling techniques to be applied to very large systems. Our own code, AIMPRO, enables the relaxation of clusters as large as 800 atoms while still maintaining full self-consistency and a realistic basis. Moreover, the use of pseudopotentials means that applications to Ge clusters are no more time consuming than those built of C. An important thrust of our work has been the computation of accurate vibrational modes of defects and this has caught the attention of several prominent experimental groups with the consequence that joint studies of rather complicated defects have been successfully made. We outline the procedures used and discuss applications that have been made to a wide variety of non-metallic systems such as vacancy defects in diamond, interstitial centres in silicon and carbon-related defects in III–V materials.