Abstract:
In this thesis, we have presentrd a comprehensive study of modeling point defects in high and low symmetry crystals with Polarizable Point Ion (PPI) model. We worked out an alternate scheme to estimating energies of point defects through finite size calculations. This new method is tested for cubic NaCl crystal and is found to agree well with other existing results. Next, we studied in detail the effect of quadrupoles in the formation energy of vacancies in alkaline earth oxides using the approximate Mott-Littleton (ML) scheme. In agreement with earlier results on AgCl and AgBr, the quadrupoles are found to have substantial effect on defect energies raising a challenge to the existing dipolar models. We then worked out the PPI firmulations for low symmetry crystals, both in perfect and defect environment. A suitable set of short range potential parameters are deduced for monoclinic...
