First Principles Studies of Electronic and Optical Properties of Transition Metal Oxide Clusters

Nanostructured clusters involving transition metal oxides constitute one of the most interesting classes of materials, as they exhibit a wide range of structures and properties that can lead to many important potential applications. From a computational perspective, transition metal oxide nanostructures present challenges for both ground state and excited state properties, due to the nature of confinement, and localized and strongly correlated nature of their d electrons. In this thesis I present results and analyses of my computations on two systems: (i) copper oxide cluster anions and (ii) building units of one of the metal organic frameworks (MOFs), IRMOF-1, and its analogues. For the copper oxide cluster anions, the photoelectron spectra of Cu2O–, CuO–, CuO2– and CuO3– clusters are calculated using density functional theory (DFT) and many-body perturbation theory within the GW approximation. My computational results and existing experimental data are systematically compared with a focus on the comparison of semi-local and hybrid functionals. The presence of self-interaction error within different levels of theories and its mitigating ways are also discussed. For the building blocks of MOFs, the geometries are optimized using DFT and absorption spectra are computed using time-dependent DFT. The gradual trends of geometric parameters and optical band gaps in the analogues of IRMOF-1 are analyzed. The transition mechanisms near the band edge are also discussed using density of states, integrated oscillator strength, and orbital characters analysis.