An analysis of the correlation energy contribution to the interaction energy of inert gas dimers.

An accurate description of electron correlation is essential for the calculation of interaction energies in cases where dispersion energy is a major component, for example, for the rare gas atoms, physisorption on graphite, and graphene-graphene interactions. Such calculations are computationally demanding using supermolecule methods and the energies calculated lack a simple, physical interpretation. Alternatively density functional theories (DFTs) may be used to give an approximate estimate of the correlation energy. However, the physical nature of this DFT estimate of electron correlation energy is not well understood and, in fact, most current DFT methods do not describe dispersion energy at all. Hence, an analysis of the correlation energy contribution to interaction energies where dispersion energy is important is needed. In order to do this we provide an analysis of the correlation energy contribution to the potential energy curves of He₂, Ne₂, and Ar₂ in terms of the Hartree–Fock (HF) interaction term ΔE_int^HF, a dispersion energy term E_disp and an electron correlation term ΔE_int^C. ΔE_int^C includes all other correlation energy effects besides E_disp and is shown to be repulsive, of a similar short range character to, but of smaller magnitude than ΔE_int^HF. This analysis was used to develop a theoretical model which gives a very good estimate of the potential energy wells for He₂, Ne₂, Ar₂, HeNe, HeAr, and NeAr. [ABSTRACT FROM AUTHOR]