A simple approach to electronic charge induction in atomistic simulations

Abstract

A scheme is presented for periodically updating atom-centered partial charges due to changing local electric fields that arise during the course of a molecular simulation. The effects of electrostatic induction, due to polarization of the local electron density of bonded atom pairs, are realized through the approximation of the bond polarizability tensor as being cylindrically symmetric and directed along the bond axis, with negligible lateral polarizability. This simplification allows the reduction of polarization effects to a scalar bond ‘polarization parameter’, and subsequent partitioning of the local electron density into charge modifiers located at atom centers. The induced charges assigned to each atom are determined self-consistently. This simplification permits a reasonable approximation of both the magnitude and direction of molecular dipole moments and of molecular polarizabilities in the case of small-molecule fluorocarbons. The model is extended to the calculation of atom-centered partial atomic charges for two conformations of poly(vinylidenefluoride). The proposed method fits well into the framework of established atomistic simulation techniques based on Coulombic nonbonded atomic interactions.