Molecular Dynamics Simulation of Surface Tension for Polar Molecules. Correction for Long-Range Interaction by Generalized van der Waals Theory.

Abstract

A new method, based on the Generalized van der Waals (GvdW) theory, for the correction of interaction truncation errors in the calculation of surface tensions from molecular dynamics simulations of polar liquids is presented and applied to SPC water. Several simulations using truncation radii ranging from 0.9 to 1.6 nm of a 4 nm thick SPC water slab are reported. The surface tension as obtained directly from the simulations grows with the cutoff from 56 to 80 mN m(-1), whereas the correction ranges from 24 to 8 mN m(-1), yielding resulting surface tensions between 74 and 88 mN m(-1) with a minimum at a truncation radius of 1.2 nm. The minimum might reflect the shell structure in the liquid and the deviation from an ideal dipole (assumed in the GvdW calculation) for the SPC model.