Accurate thermochemistry from corrected Hartree–Fock results: rapid estimation of nearly experimental quality total energy using the small 6-31G(d) basis set

Abstract.: Gaussian-3 ground-state total electronic energies have been approximated using single point 6-31G(d) basis set Harteee–Fock self-consistent-field (HF-SCF) total energies and partial charges based on our earlier rapid estimation of correlation energy from partial charges method. Sixty-five closed-shell neutral molecules (composed of H, C, N, O, and F atoms) of the G2/97 thermochemistry database were selected for the present study. The main feature in this work is that the␣basis set error has been treated by the least squares fit of rapid estimation of basis set error and correlation energy from partial charges (REBECEP) atomic parameters. With these parameters a rather accurate closed-shell ground-state electronic total energy can be obtained from a small basis set HF-SCF calculation in the vicinity of stationary points. The average absolute deviation of the best REBECEP enthalpies of formation from the experimental enthalpies of formation is 1.39 kcal/mol for the test set of 65 enthalpies of neutral molecules.