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Atomic radii in molecules for use in a polarizable force field

Authors

  • Marcel Swart,

    Corresponding author
    1. Institut de Química Computacional and Departament de Química, Universitat de Girona, Campus Montilivi, 17071 Girona, Spain
    2. Institució Catalana de Recerca i Estudis Avançats (ICREA), Pg. Lluís Companys 23, 08010 Barcelona, Spain
    • Institut de Química Computacional and Departament de Química, Universitat de Girona, Campus Montilivi, 17071 Girona, Spain
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  • Piet TH. Van Duijnen

    1. Theoretical Chemistry, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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Abstract

We report here the results for an ab initio approach to obtain the parameters needed for molecular simulations using a polarizable force field. These parameters consist of the atomic charges, polarizabilities, and radii. The former two are readily obtained using methods reported previously (van Duijnen and Swart, J Phys Chem A 1998, 102, 2399; Swart et al. J Comput Chem 2001, 22, 79), whereas here we report a new approach for obtaining atomic second-order radii (SOR), which is based on second-order atomic moments in scaled Voronoi cells. These parameters are obtained from quantum-chemistry calculations on the monomers, and used without further adaptation directly for intermolecular interactions. The approach works very well as shown here for four dimers, where high-level coupled cluster with singles and doubles, and perturbative triples (CCSD(T)) and density functional theory (DFT) Swart-Solà-Bickelhaupt functional including Grimme's dispersion correction (SSB-D) reference data are available for comparison. The energy surfaces for the three methods are very similar, which is also the case for the interaction between a water molecule with either a chloride anion or a sodium cation. These latter systems had previously been used to criticize Thole's damped point-dipole method, but here we show that with the correct use of the method, it is perfectly able to describe the intermolecular interactions. This is most obvious for the induced dipole moment as function of the chloride–oxygen distance, where the direct (discrete) reaction field results are virtually indistinguishable from those obtained at CCSD(T)/aug-cc-pVTZ. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010

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