Resolving Discrepancies in Disjoining Pressure Predictions for Liquid Nanofilms from Molecular Simulations

TL;DR

This paper identifies key factors causing discrepancies in disjoining pressure predictions for liquid nanofilms and proposes a revised method that improves accuracy by properly accounting for dispersion interactions and film thickness definitions.

Contribution

It reveals the impact of long-range dispersion and thickness definition inconsistencies on disjoining pressure calculations and introduces a corrected Peng method for better agreement with established models.

Findings

Proper treatment of dispersion interactions improves prediction accuracy.

Revised Peng method aligns with Bhatt method for Hamaker constants.

Surface tension exhibits crossover behavior due to thickness-dependent dispersion effects.

Abstract

Literature values of disjoining pressure in liquid nanofilms from different molecular simulation methods show significant discrepancies. We demonstrate that these arise from neglecting long-range dispersion interactions and inconsistent definitions of film thickness in the original Peng method. A key insight is that long-range dispersion affects surface tension in a thickness-dependent manner, increasing it at large thickness but suppressing its enhancement at small thickness due to disjoining-pressure-induced normal compression and lateral expansion. This leads to crossover behavior in the surface tension of water nanofilms. Since disjoining pressure is obtained from the derivative of surface tension with respect to thickness, this nontrivial dependence strongly impacts its accuracy. With proper treatment of dispersion interactions and a consistent thickness definition, the revised Peng method agrees with the Bhatt method and yields more accurate Hamaker constants.