Ab-initio calculations on the energetics of H2 oxidation by FeO+ using GGA+U

COMP 208

Heather J. Kulik, hjkulik@mit.edu, Damian Scherlis, damians@mit.edu, and Nicola Marzari, marzari@mit.edu. Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Rm #13-5114, Cambridge, MA 02139
Conventional ab-initio electronic structure methods often fail to provide a qualitatively correct description of spin-state energetics of systems containing transition metals. The paradigmatic reaction of the oxidation of H2 by FeO+ demonstrates the severe limitations of common DFT functionals to provide a correct description of multiplet splittings. A DFT based GGA+U approach is introduced here to predict reaction energetics with greatly-improved accuracy, as compared to benchmark calculations that use high-level MP2/MP4 and coupled-cluster approaches. The value of U, a Hubbard-like correction, is obtained in a fully ab-initio fashion using linear-response theory and is thus not a free parameter. Transition states are identified using nudged-elastic band and string methods adapted to employ GGA+U. Thanks to the efficiency of plane-wave basis set implementation, inexpensive scaling of the technique to large biochemical complexes is demonstrated.