Table 1.

Accuracy of various QM methods for predicting standard enthalpies of formation (Δ fH2980, kcal/mol) for the experimental data of 223 molecules in the G3/99 set

FunctionalMADMax (+)Max (−)
DFT
    XYG3*1.8116.67 (SF6)−6.28 (BCl3)
    M06-2X*2.9320.77 (O3)−17.39 (P4)
    M06*4.1711.25 (O3)−25.89 (C2F6)
    B2PLYP*4.6320.37 (n-octane)−8.01 (C2F4)
    B3LYP*4.7419.22 (SF6)−8.03 (BeH)
    M06-L*5.8214.75 (PF5)−27.13 (C2Cl4)
    BLYP9.4941.0 (C8H18)−28.1 (NO2)
    PBE22.2210.8 (Si2H6)−79.7 (azulene)
    LDA121.850.4 (Li2)−347.5 (azulene)
Ab initio
    HF*211.48582.72 (n-octane)−0.46 (BeH)
    MP2*10.9329.21 (Si(CH3)4)−48.34 (C2F6)
    QCISD(T)15.2242.78 (n-octane)−1.44 (Na2)
    G21.887.2 (SiF4)−9.4 (C2F6)
    G31.057.1 (PF5)−4.9 (C2F4)
  • MADs, in kcal/mol, with the largest positive error (Max(+) energy too high) and the largest negative error (Max(−) energy too low).

  • *The geometries were optimized by using B3LYP with the 6-311+G(d,p) basis set. Analytical vibrational frequencies were calculated at the same level and scaled by 0.9877 to estimate zero-point energies. Spin-orbit corrections are included. Single point calculations are performed with the 6-311+G(3df,2p) basis set.

  • Data are from ref. 28 and computed by using B3LYP/6-311+G(3df,3pd). The geometries were optimized by using B3LYP/6-31G(2df,p). Analytical vibrational frequencies were calculated at the same level and scaled by 0.9854 to estimate zero-point energies.

  • Data are from ref. 29. The QCISD(T) results were obtained by removing the empirical ″high-level corrections″ from the G3 theory to approximate the results of QCISD(full,T)/6-311+G (3d2f,2df,2p) by a series of extrapolations in both the 1-particle and many-particle spaces.