HF–CC model for atoms and molecules

Abstract

AbstractThe Hartree–Fock–Clementi–Corongiu method (HF–CC) is revisited, aiming at an unified formulation for post‐HF energy computations in atomic and molecular systems. For atomic systems new parameterizations of the HF–CC functional are proposed for the computation of atoms. The previous HF–CC molecular functional (Clementi, E.; Corongiu, G. Theochem 2001, 543, 39), revisited and recalibrated with a new optimization of the parameters, is tested with a sample of 131 molecules, including radicals, H‐bond, and van der Waals systems. The atomization energy is decomposed into “HF classic” energy (the sum of the HF nuclear electron, HF kinetic, and HF Coulomb energies), “HF exchange” energy, and correlation energy; the latter is computed with a scaling functional with atomic, covalent, ionic, and van der Waals contributions. For the sample of 131 molecules, the computed HF–CC atomization energies have an average standard deviation of 1.89 kcal/mol. The atomic and molecular components of the correlation energy are decomposed into nuclear electron, kinetic, Coulomb, and exchange contributions; these decompositions characterize the HF–CC model and are used to explain the origin of the chemical bond. Computations on van der Waals systems show the validity of the HF–CC method also for long‐range weak interactions. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002