Three additivity approximations used in GAUSSIAN-2 (G2) theory to compute effective QCISD(T)/6-311+G(3df,2p) energies for molecular systems are investigated by carrying out full QCISD(T)/6-311+G(3df,2p) calculations on the set of 125 systems used for validation [J. Chem. Phys. 94, 7221 (1991)]. The results indicate that the approximations work very well. The average absolute deviation of the full results from experiment is 1.17 kcal/mol which is close to that of G2 theory (1.21 kcal/mol). The average absolute deviation with G2 theory is only 0.30 kcal/mol. However, the cpu cost increases by a factor of 2–3.
No takes yet. Share an insight, caveat, or question.
Curtiss et al. (1992) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: