Thermodynamics of atomistic and coarse-grained models of water on nonpolar surfaces

In order to study the phenomena where interfaces play a dominant role through molecular simulations, the proper representation of the interfacial thermodynamic properties of a given model is of crucial importance. The use of coarse-grained rather than atomistic models makes it possible to simulate interfacial systems with larger time and length scales. In the present work, we compare the structure and thermodynamic behavior of one atomistic and two single-site coarse-grained models of water on nonpolar surfaces, namely, graphite and the basal plane of molybdenum disulfide. The three models interact with the surfaces through Lennard-Jones potentials parametrized to reproduce recent experimental contact angle measurements. The models form a layered structure close to the surface, which is usually observed on sufficiently attractive nonpolar substrates. However, differences in the structure and thermodynamic behavior are observed between the models. These differences are explained by certain features of the water models, such as short range tetrahedral order and liquid density fluctuations. Besides these results, the approach employed in the present study may be used to assess the ability of coarse-grained models for solid-liquid systems to represent consistent interfacial thermodynamics.