CC BY 3.0 UnportedTkatchenko, AlexandreScheffler, Matthias2025-03-032025-03-032009https://oa.tib.eu/renate/handle/123456789/18729https://doi.org/10.34657/17748We present a parameter-free method for an accurate determination of long-range van der Waals interactions from mean-field electronic structure calculations. Our method relies on the summation of interatomic C6 coefficients, derived from the electron density of a molecule or solid and accurate reference data for the free atoms. The mean absolute error in the C6 coefficients is 5.5% when compared to accurate experimental values for 1225 intermolecular pairs, irrespective of the employed exchange-correlation functional. We show that the effective atomic C6 coefficients depend strongly on the bonding environment of an atom in a molecule. Finally, we analyze the van der Waals radii and the damping function in the C6R-6 correction method for density-functional theory calculations. © 2009 The American Physical Society.enghttps://creativecommons.org/licenses/by/3.0550530AtomsCarrier concentrationElectron density measurementElectronic structureElectronsVan der Waals forcesAtom in a moleculesBonding environmentsCorrection methodsDamping functionsDensity-functional theory calculationsElectron densitiesElectronic structure calculationsExchange-correlation functionalExperimental valuesFree atomsGround-state electronsMean absolute errorsMean fieldsParameter-free methodsReference datumVan der waals interactionsVan der Waals radiusDensity functional theoryArticle