(248f) A Simple Semi-Explicit Statmech Model of Water That Captures Dynamic Solvation Interface

Molecular simulations in aqueous solution rely on either explicit water, which is computationally expensive, or implicit water, which can miss much of the interfacial physics. Here we develop a statistical mechanical model of liquid water and its interface with solutes. It has the advantages of being efficient -- because it is a computation, not a simulation -- and of capturing water's tetrahedral hydrogen bonding and spherical Lennard Jones interactions. It entails two steps. First, in Cage Water, we develop a reference state of pure water over the full liquid range vs (T, p) [Urbic, Dill, JACS, 2018]. Second, in Crust Water [Yadav et al, JPCB, 2022], we introduce a spherical solute molecule and populate the solute's surface (i.e. its crust) with these semi-explicit water molecules that we can compute efficiently. Now we further develop this model, more physically and accurately, by capturing the translational symmetry of dynamic water molecules in the first solvation shell and by introducing ions to predict solvation of charged molecules more faithfully. We think that further developments will bring this approach into computational modeling of large scale physical and biophysical simulations.