Benchmark Database of Barrier Heights for Heavy Atom Transfer, Nucleophilic Substitution, Association, and Unimolecular Reactions and its Use to Test Theoretical Methods

A benchmark database of forward and reverse barrier heights for 19 non-hydrogen-transfer reactions has\nbeen developed by using Weizmann 1 calculations, and 29 DFT methods and 6 ab initio wave-function theory\n(WFT) methods have been tested against the new database as well as against an older database for hydrogen\natom transfer reactions. Among the tested hybrid DFT methods without kinetic energy density, MPW1K is\nthe most accurate model for calculations of barrier heights. Among the tested hybrid meta DFT methods,\nBB1K and MPWB1K are the two most accurate models for the calculations of barrier heights. Overall, the\nresults show that BB1K and MPWB1K are the two best DFT methods for calculating barrier heights, followed\nin order by MPW1K, MPWKCIS1K, B1B95, MPW1B95, BHandHLYP, B97-2, mPW1PW91, and B98. The\npopular B3LYP method has a mean unsigned error four times larger than that of BB1K. Of the methods\ntested, QCISD(T) is the best ab initio WFT method for barrier height calculations, and QCISD is second\nbest, but QCISD is outperformed by the BB1K, MPWB1K, MPWKCIS1K, and MPW1K methods.