Structure and dynamics of point defects in crystalline silicon

Ab-initio theoretical methods are increasingly being used to study the prop erties of defects in covalent materials such as silicon. Static properties include potential energy surfaces, binding energies, and electronic structu res. The dynamics involve diffusion, vibrational properties, and defect rea ctions. This paper describes a powerful combination of methods used to stud y the interactions involving vacancies, self-interstitials, and impurities in Si. The methods are Hartree-Fock in molecular clusters and density-funct ional based molecular-dynamics simulations in periodic supercells. Three ex amples of applications are discussed: 1. the dissociation of interstitial H -2 molecules by vacancies and self-interstitials, and the formation of H-2* , 2. the aggregation of vacancies leading to the formation of the ring-hexa vacancy (V-6), and 3. the trapping of interstitial copper at V-6 and the or igin of the electrical activity of copper precipitates.