Date of Award
Master of Science
Density Functional Theory (DFT) is one of the very popular and versatile methods for calculations to study electronic structure, and the accuracy of DFT depends on the approximation used in the exchange-correlation functional. One of the known problems with the approximation is that the widely used density functional approximations (DFA) suffer self-interaction errors. Systems with d-electrons such as transition metal oxides often show deviation of DFT predicted behavior from experimental result. SIE tends to unphysically lower the energies of fractionally occupied state which leads to deviation from piece-wise linear behavior of total energy between two integer occupations. This leads to delocalization of the orbitals which is more apparent in d-electron systems. Fermi-Löwdin Orbital Self-Interaction Correction (FLOSIC) is a size-extensive implementation to achieve the self-interaction-free DFA [1,2]. We applied FLOSIC method in the framework of DFT to Perdew-Wang (1992) PW91 Local spin density approximation (LSDA), Perdew-Burke-Ernzerhof (PBE) Generalized gradient approximation (GGA) and the recently developed Strongly constrained and appropriately normed (SCAN) meta-GGA and test the values of dissociation energy and dipole moments of transition metal mono-oxides(CaO, ScO, TiO, VO) and magnetic exchange coupling (J) and magnetic anisotropy of copper acetate monohydrate([Cu (CH3COO)2] 2 H2O). From the study on the dissociation energies of transition metal mono-oxide molecules we find that the FLOSIC dissociation energies are underestimated with all the three functionals whereas the DFT energies are overestimated. We find that the FLOSIC dipole moments are in general larger than the experimental values. Furthermore, we also found that removing SIE using FLOSIC generally corrects the magnetic coupling constant J in the direction of more accurate methods for copper acetate monohydrate. Using the electron density obtained from the FLOSIC calculation, we observed the improvement in magnetic anisotropy parameters.
Received from ProQuest
Mishra, Prakash, "Study Of D-Electron Systems With Fermi-Lowdin Orbital Self-Interaction Correction" (2019). Open Access Theses & Dissertations. 2003.