Estimation of Atomic and Molecular Correlation Energies from the Electron Density at the Nucleus

The problem of determining electron correlation energy is of great importance in quantum chemistry and solid state physics. The origin of this problem can be traced to the Hartree-Fock approximation. It is an independent electron approximation in which the instantaneous electron-electron repulsion is replaced by an averaged electronelectron interaction in the Hamiltonian. Consequently, the Hartree-Fock ground state has a higher energy than the true ground state and the difference is defined as the correlation energy. This problem was recognized very early in the development of quantum mechanics as applied to atoms and molecules. There have been many attempts to evaluate correlation energy contribution from measurable properties in an approximation manner. Here, some of the remarkable estimations for atomic and molecular correlation energy are briefly reviewed