Verify the role of capillary-wave fluctuations in MD–cDFT discrepancies

Verify whether thermal capillary-wave fluctuations account for the discrepancy between molecular-dynamics predictions and conventional classical density functional theory predictions of the disjoining pressure in free gas nanofilms.

Background

The paper compares molecular-dynamics simulations of Lennard–Jones argon gas nanofilms with one-dimensional cDFT predictions based on the PC-SAFT equation of state and observes substantial discrepancies in the predicted disjoining pressures and Hamaker constants. The authors discuss two possible explanations: deficiencies in the underlying density functional and the omission of thermal capillary-wave fluctuations from the mean-field cDFT description. Because molecular dynamics explicitly captures interfacial fluctuations whereas conventional cDFT laterally averages the equilibrium density, the authors propose that capillary-wave fluctuations may significantly affect the film thickness and thermodynamic properties. They note that the surface-area dependence of the MD results provides supporting evidence, since reducing the lateral area suppresses long-wavelength fluctuations and improves agreement with cDFT, but direct verification of this causal explanation remains unresolved.