The M06 suite of density functionals for main group thermochemistry, thermochemical kinetics, noncovalent interactions, excited states, and transition elements: two new functionals and systematic testing of four M06-class functionals and 12 other functionals

We present two new hybrid meta exchangecorrelation functionals, called M06 and M06-2X. The M06 functional is parametrized including both transition metals and nonmetals, whereas the M06-2X functional is a highnonlocality functional with double the amount of nonlocal exchange (2X), and it is parametrized only for nonmetals.The functionals, alongwith the previously publishedM06-L local functional and the M06-HF full-Hartree–Fock functionals, constitute the M06 suite of complementary functionals. We assess these four functionals by comparing their performance to that of 12 other functionals and Hartree–Fock theory for 403 energetic data in 29 diverse databases, including ten databases for thermochemistry, four databases for kinetics, eight databases for noncovalent interactions, three databases for transition metal bonding, one database for metal atom excitation energies, and three databases for molecular excitation energies.We also illustrate the performance of these 17 methods for three databases containing 40 bond lengths and for databases containing 38 vibrational frequencies and 15 vibrational zero point energies. We recommend the M062X functional for applications involvingmain-group thermochemistry, kinetics, noncovalent interactions, and electronic excitation energies to valence andRydberg states.We recommend the M06 functional for application in organometallic Contribution to the Mark S. Gordon 65th Birthday Festschrift Issue. Electronic supplementary material The online version of this article (doi:10.1007/s00214-007-0310-x) contains supplementary material, which is available to authorized users. Y. Zhao · D. G. Truhlar (B) Department of Chemistry and Supercomputing Institute, University of Minnesota, 207 Pleasant Street S.E., Minneapolis, MN 55455-0431, USA e-mail: [email protected] and inorganometallic chemistry and for noncovalent interactions.