(289e) Towards More Accurate Reaction Enthalpies With DFT+U Linear Response Methods

Xu, Z., Carnegie Mellon University
Kitchin, J. R., Carnegie Mellon University

It is now commonly accepted that the Hubbard U must be applied to standard DFT LDA/GGA calculations (DFT+U) to more accurately describe the electronic structure and total energy of highly correlated materials. The most notable materials that need this treatment are transition metals and their corresponding oxides. However, the methodology for applying the Hubbard U is no trivial matter, and typically a single U is picked for a variety of different systems in a single study. In this study, we propose a reaction specific U method that uses the linear response calculated U to increase the accuracy of the relative stability between transition metal oxides in different oxidation states. This method relates the empirically found reaction specific U to differences in the calculated linear response U of the reduced reactant and oxidized product. It was found that for vanadium, manganese, and iron oxide systems, the magnitude of U one needs to apply to a specific oxidation reaction is positively correlated with difference in the linear response U between the reduced reactant and oxidized product. These correlations provide us an approach for choosing a reaction specific U to improve the accuracy of reaction enthalpies for new reactions we wish to investigate using DFT+U.