Study of molecular properties in inorganic and combustion chemistry employing coupled cluster and density functional methods

Abstract

Reactions on the C₃H₅ potential energy surface (PES) were investigated using the coupled cluster methodology with an unrestricted Hartree-Fock reference wavefunction. Accurate energetics of the reactions on the PES was obtained, within the focal point scheme, using correlation treatments as extensive as coupled cluster with perturbative quadruple excitations [CCSDT(Q)]. The computed barrier heights should enable future studies of C₃H₅ species and related systems which are of critical importance in combustion chemistry. In another study, density functional theory (DFT) was employed to understand the role of hydrogen bonding in NiN₂S₂ complexes related to Nickel Superoxide Dismutase (Ni-SOD). Analysis of molecular orbital compositions, natural charges and point electrostatic potentials provide insights into the significance of H-bonding in assisting nickel based oxidation as opposed to thiolate oxidation in Ni-SOD models. Finally, the metal-metal and metal-ligand equilibrium bond distances of six transition metal compounds were computed using DFT with small, medium and large basis sets. The general reliability of small basis sets, such as the Hood-Pitzer sets, for predicting structural parameters were investigated in the study.