The coarse-grained model for a water/oil/solid system: based on the correlation of water/air and water/oil contact angles

Abstract

The coarse-grained molecular dynamics (CG MD) simulation has become an important tool for studying water/oil/solid systems which are closely related to a broad range of scientific issues, such as nanotechnology, industrial applications, and environmental sciences. However, the coarse-grained force field (CG FF) for these systems, which plays a crucial role in molecular dynamic simulation, has not been accurately established. In this work, a novel method is provided to build a coarse-grained model for molecular simulation of water/oil/solid systems. The water/oil CG FF of a pre-selected analytical form was parameterized to match thermo-dynamic quantities in combination with all-atom (AA) simulation results. Upon tuning the CG FF parameters between water and solid, solid surfaces of different wettability were obtained. Then CG FF between oil and solid of different wettability was obtained based on the correlation between water/air and water/oil contact angles. We used our CG model to simulate the water/oil spontaneous capillary displacement, which demonstrates the consistency between theory and CG MD simulation. The novel method provided here is expected to promote the development of CG FF, and the study of multiphase systems.