Parameterization of Molybdenum Disulfide Interacting with Water Using the Free Energy Perturbation Method

Abstract

Water contact angles (WCA) are often used to parametrize force field parameters of novel 2D nanomaterials, such as molybdenum disulfide (MoS2), which has emerged as a promising nanomaterial in many biomedical applications due to its unique and impressive properties. However, there is a wide range of water-MoS2 contact angles in the literature depending on the aging process on the surface of a MoS2 nanosheet and/or substrate material. In this study, we revisit and optimize existing parameters for the basal plane of MoS2 with two popular water models, TIP3P and SPC/E, using the wide range of WCAs from various experiments. We develop and deploy the free energy perturbation method for parametrizing MoS2 with experimentally determined WCAs for both fresh and aged surfaces. Energy decomposition analysis on the simulation trajectories reveals that MoS2-water interaction is dominated by van der Waals interaction, which mainly comes from the top layer of MoS2. We conclude that to describe both fresh and aged MoS2 surfaces it is convenient to only adjust the Lennard-Jones parameter ϵS (the depth of the potential well of a sulfur atom), which displays a surprisingly linear correlation with WCAs.