title: Assessment of range-separated time-dependent density-functional theory for calculating C6 dispersion coefficients.
abstract: We assess a variant of linear-response range-separated time-dependent density-functional theory (TDDFT), combining a long-range Hartree-Fock (HF) exchange kernel with a short-range adiabatic exchange-correlation kernel in the local-density approximation (LDA) for calculating isotropic C6 dispersion coefficients of homodimers of a number of closed-shell atoms and small molecules. This range-separated TDDFT tends to give underestimated C6 coefficients of small molecules with a mean absolute percentage error of about 5%, a slight improvement over standard TDDFT in the adiabatic LDA which tends to overestimate them with a mean absolute percentage error of 8%, but close to time-dependent Hartree-Fock which has a mean absolute percentage error of about 6%. These results thus show that introduction of long-range HF exchange in TDDFT has a small but beneficial impact on the values of C6 coefficients. It also confirms that the present variant of range-separated TDDFT is a reasonably accurate method even using only a LDA-type density functional and without adding an explicit treatment of long-range correlation.
authors.affiliation: Laboratoire de Chimie Théorique, Université Pierre et Marie Curie and CNRS, 75252 Paris, France. julien.toulouse@upmc.fr
authors.forename: Julien
authors.initials: J
authors.lastname: Toulouse
authors.forename: Elisa
authors.initials: E
authors.lastname: Rebolini
authors.forename: Tim
authors.initials: T
authors.lastname: Gould
authors.forename: John F
authors.initials: JF
authors.lastname: Dobson
authors.forename: Prasenjit
authors.initials: P
authors.lastname: Seal
authors.forename: János G
authors.initials: JG
authors.lastname: Ángyán