Immediate estimation of correlation energy for molecular systems from the partial charges on atoms in the molecule Original Research Article

In the authorʹs previous work (Chem. Phys. Lett. 247 (1995) 101 and Chem. Phys. Lett. 256 (1996) 229) a simple quasi-linear relationship was introduced between the number of electrons, N, participating in any molecular system and the correlation energy: −0.035 (N − 1) > Ecorr[hartree] > − 0.045(N −1). This relationship was developed to estimate more accurately correlation energy immediately in ab initio calculations by using the partial charges of atoms in the molecule, easily obtained after Hartree-Fock self-consistent field (HF-SCF) calculations. The method is compared to the well-known B3LYP, MP2, CCSD and G2M methods. Correlation energy estimations for negatively (−1) charged atomic ions are also reported.