Stability and structure of nanometer-thin perfluoropolyether films using molecular simulations

Methods to determine the stability of thin films are needed to ensure that lubricating layers maintain their integrity and so can reliably protect and lubricate moving interfaces. Here, we compare two models of perfluoropolyether and various methods of calculating disjoining pressure as a means of characterizing stability using molecular dynamics simulation. As has been shown previously, we find that energy methods, based on the variation of film-substrate interaction energy with film thickness, provide a good estimate of disjoining pressure. Further, we find that more rapid computational methods based on the density in the film, though they may yield a poorer estimate of the magnitude of the disjoining pressure, yield correct predictions for thin film stability.