Density Functional Theory in Transition-Metal Chemistry: A Self-Consistent HubbardUApproach

Transition-metal centers are the active sites for a broad variety of biological and inorganic chemical reactions. Notwithstanding this central importance, density-functional theory calculations based on generalized-gradient approximations often fail to describe energetics, multiplet structures, reaction barriers, and geometries around the active sites. We suggest here an alternative approach, derived from the Hubbard $U$ correction to solid-state problems, that provides an excellent agreement with correlated-electron quantum chemistry calculations in test cases that range from the ground state of ${\mathrm{Fe}}_{2}$ and ${\mathrm{Fe}}_{2}^{\ensuremath{-}}$ to the addition elimination of molecular hydrogen on ${\mathrm{FeO}}^{+}$. The Hubbard $U$ is determined with a novel self-consistent procedure based on a linear-response approach.