Density Functional Theory in Transition Metal Chemistry: A Self-Consistent Hubbard U approach

Transition metals ions are reactive centers for a broad variety of biological and inorganic chemical reactions. Despite this central importance, density functional theory calculations based on local density or generalized gradient approximations (GGA) often fail qualitatively and quantitatively to describe multiplet splittings, relaxed structures, and reaction barriers for these systems. We have recently proposed$^{1}$ augmenting the GGA functional with a Hubbard U which is obtained from a self-consistent linear response procedure. This fully ab initio GGA+U approach provides excellent agreement with accurate, correlated-electron quantum chemistry calculations for paradigmatic cases that include the ground state of the iron dimer and addition-elimination reactions on bare FeO$^+$. We also show how a GGA+U approach may be applied to large-scale biological systems by preserving the favorable scaling of traditional density functional approaches with improved accuracy. 1) H. J. Kulik, M. Cococcioni, D. Scherlis and N. Marzari, PRL (2006).