Solid–liquid interfaces in MARTINI 3: Modeling approaches and the case study of silica surfaces in water

The MARTINI force field has become increasingly popular in material science by virtue of its versatility and its building block approach. However, force field parametrization is primarily based on reproducing structural and thermodynamic properties of the building blocks in solution, which may not be the most suitable strategy for regular, extended surfaces at solid–liquid interfaces, e.g., the planar facets of nanoparticles. In this study, we propose a novel strategy for simulating MARTINI planar surfaces in contact with liquids. While the choice of bead types in MARTINI models for molecules and ions in solution is often dictated by their chemistry, we suggest that surface–liquid interactions can be refined through a top-down approach. Specifically, we propose tuning the density of particles in the model surface to reproduce available experimental data on contact angles. In addition, we suggest several possible solutions to mitigate an artifact of the force field, that is, the excessive ordering of the liquid in contact with regular surfaces. We implement our strategy in the development of three distinct silica surfaces: a hydrophobic silica surface functionalized with organosilanes, a moderately hydrophilic bare quartz surface, and an amorphous silica surface fully wetted by water.