Table 2.

Accuracy of various QM methods for energy barriers

FunctionalAll (76)HT38HAT12NS16UM10
DFT
    XYG3*1.020.751.381.420.98
    M06-2X1.201.131.611.220.92
    B2PLYP*1.941.813.062.160.73
    M062.132.003.381.781.69
    M06-L3.884.165.933.581.86
    B3LYP*4.284.238.493.252.02
    BLYP8.237.5214.668.403.51
    PBE8.719.3214.936.973.35
    LDA14.8817.7223.388.505.90
Ab initio
    HF11.2813.6616.876.673.82
    MP24.574.1411.760.745.44
    QCISD(T)1.101.241.211.080.53
  • MADs in kcal/mol for the 76 reactions in the Truhlar database web site (14, 15, 33), which contains the best available ab initio reference data for reaction barrier heights. Here, HT38 refers to the forward and reverse barrier heights for 19 hydrogen transfer reactions; HAT12 refers to the forward and reverse barrier heights for 6 heavy-atom transfer reactions, NS16 refers to the forward and reverse barrier heights for 8 nucleophilic substitution reactions, and UM10 refers to the forward and reverse barrier heights for 5 association and unimolecular reactions.

  • *Our calculations used the 6-311+G(3df,2p) basis sets with geometries from the Truhlar database web site.

  • Data are from refs. 14 and 15.

  • Data are from ref. 33.