Molecular Dynamics Exploration of Thin Liquid Films on Solid Surfaces. 1. Monatomic Fluid Films

Abstract

The thickness of the interfacial region dividing bulk liquid and vapor regions is typically on the order of a few molecular diameters. Furthermore, in systems where the characteristic length scale is the same order of magnitude as the thickness of the interface such as a thin liquid film on a solid surface, behavior may be different than that for larger systems. The small thickness of such films leads to difficult experimental observation of phenomena within various regions of the film: the wall-affected region, the bulk liquid, and the liquid–vapor interfacial region. A hybrid simulation methodology is applied that combines a deterministic molecular dynamics simulation of the liquid regions with a stochastic treatment of the far-field vapor region boundary. In this simulation scheme, the imposed far-field pressure may be held fixed or iterated as the simulation is advanced in time until the mass in the system stabilizes at the specified temperature, which establishes the equilibrium saturation vapor pressure for the specified temperature as dictated by the intermolecular force interaction models for the fluid and molecules near the solid surface. Simulation results are presented for an argon liquid film on a solid metallic surface.