Ab initio Hartree-Fock and many body perturbation theory calculation of the energies of the excited states of some materials

Abstract

In this thesis the use of the Unrestricted Hartree-Fock technique augmented by many body perturbation theory techniques and symmetry projection methods in the study of the energies of the excited states of atomic, molecular and solid state systems is investigated. A perturbation method for finding relativistic corrections to the energy is also investigated. Results are presented which indicate that many body perturbation theory substantially improves Hartree-Fock energies, that symmetry projection enables one to calculate the energies of excited state singlets, and that one can compute relativistic corrections for free atoms but one cannot compute enhancement effects in the spin-orbit parameter due to atomic overlap in solids.