Oxidation energies of transition metal oxides within the GGA+U framework

The energy of a large number of oxidation reactions of 3d transition metal oxides is computed using the generalized gradient approach GGA and GGA+U methods. Two substantial contributions to the error in GGA oxidation energies are identified. The first contribution originates from the overbinding of GGA in the O2 molecule and only occurs when the oxidant is O2. The second error occurs in all oxidation reactions and is related to the correlation error in 3d orbitals in GGA. Strong self-interaction in GGA systematically penalizes a reduced state with more d electrons over an oxidized state, resulting in an overestimation of oxidation energies. The constant error in the oxidation energy from the O2 binding error can be corrected by fitting the formation enthalpy of simple nontransition metal oxides. Removal of the O2 binding error makes it possible to address the correlation effects in 3d transition metal oxides with the GGA+U method. Calculated oxidation energies agree well with experimental data for reasonable and consistent values of U.