Quantum and quantum-classical calculations of core-ionized molecules in varied environments

Computational quantum chemistry methods have been applied in two particular cases: to provide insight to photoionization induced fragmentation of HgBr2 and HgCl2 molecules, and to study core-electron binding energies and chemical shifts of molecules in liquid, surface adsorbed and polymeric environments in the framework of quantum mechanics/molecular mechanics (QM/MM). In the photodissociation studies the computational work is based on the relativistic Dirac equation as the systems present strong spin-orbit interaction affecting the fragmentation processes. In the QM/MM studies of ethanol-water mixtures and molecules physisorbed on silver surfaces the structures are provided by classical molecular dynamics simulations to analyze the distribution of the binding energies of core-orbitals and effects of their surroundings. In the case of polymethyl methacrylate polymer the impact of a QM-MM boundary and a polymeric environment are studied. The theoretical backgrounds of the computational methods applied and the obtained results are discussed. ; This thesis is for a double degree PhD done in KTH Royal institute of Technology and University of Oulu. QC 20180502