New insights into the properties determining oxygen vacancy formation energies in oxides.

摘要

Oxygen vacancy formation energies play a fundamental role in a broad range of important energy applications; nevertheless, predictive understanding of the properties of metal oxides that determine such energetics remains incomplete. We use modern, electronic structure theory and solid state defect models to demonstrate a fundamental and unifying set of intrinsic bulk material properties which serve as accurate descriptors of oxygen vacancy formation energies across a wide variety of oxides spanning a range of different crystal structures. This thesis work shows oxygen vacancy formation energies increase with increasing metal-oxygen bond strength and/or increasing oxygen vacancy electron redistribution energy. Here, the bond strength contribution is closely related to the oxide enthalpy of formation and the electron redistribution energy contribution is described by either the band gap energy or, for small band gap materials, by the energy difference between the lowest unoccupied state and the O 2p band center. Our findings i) provide a valuable method for efficiently predicting oxygen vacancy formation energies from intrinsic bulk material properties and ii) extend our understanding of the dominant physical mechanisms contributing to oxygen vacancy formation energies thereby better enabling the design of new redox active materials.