3 Mn (") + 2O $ (&) ↔ Mn ' O ( ∆H = -1387.8 kJ/mol [5] Previously reported DFT energy correction schemes have minimized errors by using computationally-expensive hybrid functionals, fitting U eff , mixing GGA and GGA+U energies, and fitting elemental reference energies. Other strategies have included fitting the DFT-computed energy of O 2 to reproduce the formation energies of binary oxides or of water. We chose a synergistic strategy of fitting U eff (discussed below), adjusting the Mn reference energy, and referencing the energy of O 2 to the formation energy of water. Similar schemes have been shown to compare favorably for the formation of high fidelity Pourbaix diagrams. Our scheme also keeps bulk DFT calculations maximally compatible with surface calculations.