The implementation of transition-metal oxides in clean energy applications requires the precise characterization of multiple properties of those materials, such that materials selection processes can appropriately choose materials for particular applications. One of the most extensive sets of properties required in materials characterization for these applications consists of the reaction energetics involving those materials, such as the oxygen vacancy formation energetics of perovskites and the formation energetics associated with phase transformations between different metal oxide polymorphs. In order to select a material for a particular application that satisfies multiple criteria associated with several properties, a large materials set should be considered, the size of which can be constrained by the expense of experimental procedures used to calculate those material properties. In order to address this concern, computational studies can be completed via the first-principles method of Density Functional Theory (DFT), which can be implemented to both calculate the values of experimentally known material properties within precision and – using the methodologies for calculating these known properties – predict the values of material properties for which adequate experimental data is unavailable. Given that comprehensive knowledge of error sources affecting the calculation of known and prediction of unknown material properties in DFT is not available, the validation of calculations of known materials is assessed with precision criteria involving relative energetics, determining the impact of accounting for potential error sources on relative energetic ordering to assess their significance.
In this thesis, the prediction of largely unknown oxygen vacancy formation energetics of perovskite materials is completed within the criterion of relative energetic ordering of adjacent systems in energetic trends, evaluating the impact of oxygen vacancy concentration, crystal structure, magnetism, and electronic structure method variation on those trends. Given known information on the relative energetic ordering of TiO2 polymorphs, the impact of varying pseudopotentials, functionals, and other factors in energetic trends is also evaluated. Using previously resolved information concerning the identification of errors in perovskite and BO2 polymorph systems, the evaluation of differences between calculated and experimental formation energies of a broader set of binary metal oxide systems featuring transition or rare earth metal cations with incomplete d or f-shells was completed, in order to evaluate the physical or first-principles causes affecting multiple systems within that set.
|School:||Carnegie Mellon University|
|School Location:||United States -- Pennsylvania|
|Source:||DAI-B 77/07(E), Dissertation Abstracts International|
|Subjects:||Physical chemistry, Chemical engineering, Materials science|
|Keywords:||Density functional theory, Formation energy, Hubbard U model, Linear response theory, Relational database, Semiconductors|
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