title: Minimal Basis Iterative Stockholder: Atoms in Molecules for Force-Field Development.
abstract: Atomic partial charges appear in the Coulomb term of many force-field models and can be derived from electronic structure calculations with a myriad of atoms-in-molecules (AIM) methods. More advanced models have also been proposed, using the distributed nature of the electron cloud and atomic multipoles. In this work, an electrostatic force field is defined through a concise approximation of the electron density, for which the Coulomb interaction is trivially evaluated. This approximate "pro-density" is expanded in a minimal basis of atom-centered s-type Slater density functions, whose parameters are optimized by minimizing the Kullback-Leibler divergence of the pro-density from a reference electron density, e.g., obtained from an electronic structure calculation. The proposed method, Minimal Basis Iterative Stockholder (MBIS), is a variant of the Hirshfeld AIM method, but it can also be used as a density-fitting technique. An iterative algorithm to refine the pro-density is easily implemented with a linear-scaling computational cost, enabling applications to supramolecular systems. The benefits of the MBIS method are demonstrated with systematic applications to molecular databases and extended models of condensed phases. A comparison to 14 other AIM methods shows its effectiveness when modeling electrostatic interactions. MBIS is also suitable for rescaling atomic polarizabilities in the Tkatchenko-Scheffler scheme for dispersion interactions.
authors.affiliation: Center for Molecular Modeling (CMM), Member of the QCMM Ghent-Brussels Alliance, Ghent University , Technologiepark 903, B9000 Ghent, Belgium.
authors.forename: Toon
authors.initials: T
authors.lastname: Verstraelen
authors.affiliation: Center for Molecular Modeling (CMM), Member of the QCMM Ghent-Brussels Alliance, Ghent University , Technologiepark 903, B9000 Ghent, Belgium.
authors.forename: Steven
authors.initials: S
authors.lastname: Vandenbrande
authors.affiliation: Department of Chemistry and Chemical Biology, McMaster University , 1280 West Main Street, Hamilton, Ontario L8S 4M1, Canada.
authors.forename: Farnaz
authors.initials: F
authors.lastname: Heidar-Zadeh
authors.affiliation: Center for Molecular Modeling (CMM), Member of the QCMM Ghent-Brussels Alliance, Ghent University , Technologiepark 903, B9000 Ghent, Belgium.
authors.forename: Louis
authors.initials: L
authors.lastname: Vanduyfhuys
authors.affiliation: Center for Molecular Modeling (CMM), Member of the QCMM Ghent-Brussels Alliance, Ghent University , Technologiepark 903, B9000 Ghent, Belgium.
authors.forename: Veronique
authors.initials: V
authors.lastname: Van Speybroeck
authors.affiliation: Center for Molecular Modeling (CMM), Member of the QCMM Ghent-Brussels Alliance, Ghent University , Technologiepark 903, B9000 Ghent, Belgium.
authors.forename: Michel
authors.initials: M
authors.lastname: Waroquier
authors.affiliation: Department of Chemistry and Chemical Biology, McMaster University , 1280 West Main Street, Hamilton, Ontario L8S 4M1, Canada.
authors.forename: Paul W
authors.initials: PW
authors.lastname: Ayers