Perturbation calculations of the interaction energy between closed-shell Hartree-Fock atoms

Abstract

Interaction energy between two neon atoms described by the HartreeFock wavefunctions has been calculated through the second order of the symmetry-adapted perturbation theory. Particular contributions, the first order energy, dispersion, induction, exchange-dispersion and exchangeinduction energies, are analysed and the basis set effects are discussed. The calculated values of the interaction energies are close to the experimental energies.

Weak interactions between small systems. Models for studying the nature of intermolecular forces and challenging problems for ab initio calculations

“…The interaction energy obtained by considering in eq 12 the corrections of the zeroth order in W only may be termed "the interaction energy between Hartree-Fock systems". 56 The intramonomer correlation effects may be allowed for by calculating the remaining corrections.12 However, in the second and higher orders with respect to V, some of the intramonomer correlation corrections can be obtained by using the time-dependent coupled Hartree-Fock57 polarization propagator. 58 For this reason these corrections are sometimes termed the "apparent intramolecular correlation".…”

“…98 Later, however, it was found that the sum of the induction and exchange induction contributions failed to reproduce the mutual deformation effect arising at the SCF level between closed-shell atoms. 56,96,99,100 This fact was attributed to the weak symmetry forcing applied in the exchange polarization term.101,102 It turned out that exchange effects are crucial in the mutual deformation of closed-shell atoms and ions.102,103 These effects can be accounted for only by an exchange perturbation formalism with strong symmetry forcing.101 (Strong symmetry forcing, as opposed to weak symmetry forcing, considers symmetry constraints and electrostatic effects simultaneously.12) It is still not clear whether the exchange dispersion term suffers from the same problem.…”

Tunable far infrared laser spectroscopy of van der Waals bonds: Ar-NH sub 3

“…The main scheme has been the double perturbation theory [38][39][40][41][42], which estimates some intra-subunit correlation effects (38]. How physically meaningful these mathematical results are still remains an important question.…”