Performance of the RB3-LYP, RMP2, and UCCSD(T) procedures in calculating radical stabilization energies for NHX radicals

N-H bond dissociation energies (BDEs) and radical stabilization energies (RSEs) associated with the *NHCF3, *NHCHO, *NHCOCH3, and *NHCONH2 radicals have been calculated at a number of theoretical levels. These include UHF, RHF, UB3-LYP, RB3-LYP, UMP2, RMP2, UCCSD(T), and URCCSD(T) with a variety of basis sets, as well as the high-level composite methods W1, CBS-QB3, and G3X(MP2)-RAD. For these systems, particular care must be taken to ensure convergence to the lowest-energy solution of the self-consistent-field (SCF) equations. We have assessed the performance of the various levels of theory in calculating the BDEs and RSEs of the *NHX radicals and find that, although there are somewhat larger errors for the simpler methods, the performance generally parallels that observed previously for *CH2X radicals. In particular (and in contrast to a recent report), RB3-LYP and UCCSD(T) consistently produce very good RSEs for *NHX radicals, provided that the lowest-energy solutions are correctly identified. The RMP2 RSEs, while not as good as those for *CH2X radicals, do not show the previously claimed large errors.