Self-Consistent-Charge Density-Functional Tight-Binding (SCC-DFTB) Parameters for Ceria in 0D to 3D

Reducible oxides such as CeO2 are challenging to describe with standard density-functional theory (DFT) due to the mixed valence states of the cations; they often require the use of non-standard correction schemes, and/or more computationally expensive methods. This adds a new layer of complexity when it comes to the generation of Slater-Koster tables and the corresponding repulsive potentials for self-consistent density-functional based tight-binding (SCC-DFTB) calculations of such materials. In this work, we provide guidelines for how to set up a parametrization scheme for mixed valence oxides within the SCC-DFTB framework, with a focus on reproducing structural and electronic properties as well as redox reaction energies calculated using a reference DFT method. This parametrization procedure was here used to generate parameters for Ce-O systems, with Ce in its +III or +IV formal oxidation states. The generated parameter set is validated by comparison with DFT calculations for various ceria (CeO2) and reduced ceria (CeO2-x) systems of different dimensionalities ranging from 0D (nanoparticles) to 3D (bulk). As oxygen vacancy defects in ceria are of crucial importance to many technological applications, special focus is directed toward the capability of describing such defects accurately.