Effects of Concentration, Crystal Structure, Magnetism, and Electronic Structure Method on First-Principles Oxygen Vacancy Formation Energy Trends in Perovskites

Systematic prediction of the redox reaction energetics of large sets of 3d transition metal oxides is imperative to the selection of oxygen carrier candidates in applications ranging from chemical looping to solid oxide fuel cell (SOFC) cathode design. In particular, the energetic study of oxygen vacancy formation in unmixed perovskites with La, alkali, and alkaline A-site metal cationsas well as 3d transition metal B-site cationsis a crucial first step in understanding the energetic tunability afforded by cation doping in ABO(3) materials. An assessment of the relative oxygen vacancy formation energetics of LaBO3, SrBO3, and similar materials that serve as a guideline for predicting energetics in related systems is completed below using density functional theory (DFT). This assessment illustrates which simplifications can be made in the prediction of energetics trends without affecting trend order. The independent consideration of oxygen vacancy concentration, crystal structure, and antiferromagnetic (AFM) magnetism revealed that these factors in DFT calculations had no effect on trend order. However, the ferromagnetic (FM) SrBO3 trend order was affected between SrMnO3 and SrFeO3 as a function of defect concentration. Moreover, energetic trends were also formed by adding constant, incremental values of the Hubbard U parameter contributing to the 3d orbitals of perovskite B-sites. Calculation of U parameters was done by linear response theory or by a literature review of previous research.