title: Dispersion interactions in density-functional theory: an adiabatic-connection analysis.
abstract: We present an analysis of the dispersion interaction energy and forces in density-functional theory from the point of view of the adiabatic connection between the Kohn-Sham non-interacting and fully interacting systems. Accurate coupled-cluster singles-doubles-perturbative-triples [CCSD(T)] densities are computed for the helium dimer and used to construct the exchange-correlation potential of Kohn-Sham theory, showing agreement with earlier results presented for the Hartree-Fock-Kohn-Sham method [M. Allen and D. J. Tozer, J. Chem. Phys. 117, 11113 (2002)]. The accuracy of the methodology utilized to determine these solutions is checked by calculation of the Hellmann-Feynman forces based on the Kohn-Sham densities, which are compared with analytic CCSD(T) forces. To ensure that this comparison is valid in a finite atomic-orbital basis set, we employ floating Gaussian basis functions throughout and all results are counterpoise corrected. The subtle charge-rearrangement effects associated with the dispersion interaction are highlighted as the origin of a large part of the dispersion force. To recover the exchange-correlation components of the interaction energy, adiabatic connections are constructed for the supermolecular system and for its constituent atoms; subtraction of the resulting adiabatic-connection curves followed by integration over the interaction strength recovers the exchange-correlation contribution relevant to the density-functional description of the dispersion interaction. The results emphasize the long-ranged, dynamically correlated nature of the dispersion interaction between closed-shell species. An alternative adiabatic-connection path is also explored, where the electronic interactions are introduced in a manner that emphasizes the range of the electronic interactions, highlighting their purely long-ranged nature, consistent with the success of range-separated hybrid approaches in this context.
authors: Department of Chemistry, Centre for Theoretical and Computational Chemistry, University of Oslo, P.O. Box 1033, Blindern, Oslo N-0315, Norway.
authors: Marie D
authors: MD
authors: Strømsheim
authors: Naveen
authors: N
authors: Kumar
authors: Sonia
authors: S
authors: Coriani
authors: Espen
authors: E
authors: Sagvolden
authors: Andrew M
authors: AM
authors: Teale
authors: Trygve
authors: T
authors: Helgaker
mesh_terms: D006371:Helium / Q000737:chemistry; D011789:Quantum Theory
chemical_list: D006371:Helium