Transferable Potential Function for Flexible H$_2$O Molecules Based on the Single Center Multipole Expansion

Abstract

A potential function describing a system of flexible water molecules based on a single center multipole expansion of the electrostatic interactions is described, denoted f-SCME. The potential function includes a quadrupole moment surface (QMS) that reproduces results of high level configuration interaction calculations in addition to the commonly used dipole moment surface (DMS) developed by Partridge and Schwenke.The use of the so-called M-site models based on the DMS atomic charges to represent the QMS is explored, and some improvements presented. The potential function also includes the static octupole and hexadecapole moments and anisotropic dipole-dipole, dipole-quadrupole and quadrupole-quadrupole polarizability tensors as well as dispersion interaction of the original rigid SCME potential [SCME, Wikfeldt et al, PCCP