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Analysis of Functional Models in Density Functional Theory : Applications to Transition Metal Oxides

dc.contributor.advisorMoewes, Alexen_US
dc.contributor.committeeMemberBourassa, Adamen_US
dc.contributor.committeeMemberChang, Gap Sooen_US
dc.contributor.committeeMemberMueller, Jensen_US
dc.creatorKerpan, Tyrelen_US
dc.date.accessioned2014-01-21T19:01:25Z
dc.date.available2014-01-21T19:01:25Z
dc.date.created2013-09en_US
dc.date.issued2013-10-11en_US
dc.date.submittedSeptember 2013en_US
dc.description.abstractThis work presents a study of the electronic structure of four transition metal oxides (TMOs) using spectroscopic data and a variety of theoretical models. TMOs are a class of materials made from d-block metals in the periodic table, and one or more oxygen atoms. The nature of d-electrons is examined and theoretical models used to treat d-electron systems are tested against experimental data. Background theory of condensed matter physics is outlined. An overview of density functional theory (DFT) as a theoretical model for calculating the electronic structure of materials is presented. A variety of exchange-correlation (XC) functionals used within the DFT framework are outlined and tested for their applicability to the TMO systems in question. X-ray spectroscopy is briefly outlined and used to test the validity of the different XC functionals. All four compounds, AgO, Ag2O, CuO, and Cu2O require a Hubbard U term in the XC functional to most accurately reproduce experimental results. The effects of varying the value of U is examined in depth. The oxygen K-edge X-ray emission spectra (XES) exhibits a“two peak” structure for all compounds; the effect of varying the U value is to change the intensity ratio of the two peaks. The ratio of the two peaks as a function of U shows a linear trend in all compounds. A simple line is fit to the peak ratio vs. U curve. A common line between all compounds would provide an important metric with which to predict the appropriate U value needed in similar materials based on simple experimental data. However, the parameters of the fitted line were not common between the four compounds and any metric derived from this method would be system-dependent and not widely applicable to other systems. There are, however, interesting trends in the data when the U value is varied that provide subjects for future research. A number of fundamental quantities are determined both from experiment and theoretical calculations. Calculated bandgap values are shown to be lower than the experimental values for most functionals tested. This is not unexpected as DFT methods are known to predict much smaller bandgaps than expected. The Heyd-Scuseria-Ernzerhof (HSE) functional used for Ag2O and Cu2O does predict the bandgaps very accurately. The core-hole effect is estimated and proven to be negligible in these systems. Charge transfer and on-site Coulomb repulsion energies, important quantities in the electronic behaviour of TMOs, are determined and compared to previously reported values.en_US
dc.identifier.urihttp://hdl.handle.net/10388/ETD-2013-09-1248en_US
dc.language.isoengen_US
dc.subjectDensity Functional Theoryen_US
dc.subjectTransition Metal Oxidesen_US
dc.subjectX-ray Spectroscopyen_US
dc.subjectHubbard Uen_US
dc.subjectd-electronsen_US
dc.subjectCorrelated Materialsen_US
dc.subjectElectronic Structureen_US
dc.subjectDensity of Statesen_US
dc.titleAnalysis of Functional Models in Density Functional Theory : Applications to Transition Metal Oxidesen_US
dc.type.genreThesisen_US
dc.type.materialtexten_US
thesis.degree.departmentPhysics and Engineering Physicsen_US
thesis.degree.disciplinePhysicsen_US
thesis.degree.grantorUniversity of Saskatchewanen_US
thesis.degree.levelMastersen_US
thesis.degree.nameMaster of Science (M.Sc.)en_US

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