Abstract:
This thesis investigates the electronic excitations of titanium dioxide (TiO2), iridium dioxide (IrO2), and tin dioxide (SnO2), which are key materials for photocatalysis and photovoltaics. To perform this study, we used advanced computational methods, such as Density Functional Theory (DFT) and Green’s function approach within the GW approximation. We studied the rutile and anatase phases of TiO2 and SnO2, as well as the rutile phase of IrO2 by calculating their electronic properties at the DFT level. For SnO2, we went also beyond DFT by calculating quasiparticle excitations within the GW approximation, discussing the role of pseudopotential description.The exchange correlation function was described using the local density approximation (LDA) and the Perdew-Burke-Ernzerhof (PBE) which is one of the most commonly used parameterizations of the generalized gradient approximation (GGA). The structural parameters of the dioxides are found to be in a fair agreement with the experimental values and previous calculations for all oxides. The band gaps obtained are also in fair agreement with the previous DFT calculations although there is still a big gap between the DFT band gap ( EDFT Gap ) and experimental gap. The self-consistent GW band gap (EGW Gap ) for rutile SnO2 , i.e, 3.81 is in better agreement with both previous studies and experiments , i.e, 3.56 compared to G0W0 band gap , i.e, 3.08.
