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

Water contact angles (WCA) are often used to parametrize force field parameters of novel 2D nanomaterials, such as molybdenum disulfide (MoS), 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-MoS contact angles in the literature depending on the aging process on the surface of a MoS nanosheet and/or substrate material. In this study, we revisit and optimize existing parameters for the basal plane of MoS 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 MoS with experimentally determined WCAs for both fresh and aged surfaces. Energy decomposition analysis on the simulation trajectories reveals that MoS-water interaction is dominated by van der Waals interaction, which mainly comes from the top layer of MoS. We conclude that to describe both fresh and aged MoS surfaces it is convenient to only adjust the Lennard-Jones parameter ε (the depth of the potential well of a sulfur atom), which displays a surprisingly linear correlation with WCAs.