An Extended Energy-Biased Aggregation-Volume-Bias Monte Carlo (EB-AVBMC) Method for Nucleation Simulation of a Reactive Water Potential.

The aggregation-volume-bias Monte Carlo (AVBMC) algorithm has been widely used with empirical water models like TIP3P, SPC/E, TIP4P, and TIP4P/2005 to study nucleation and vapor-liquid properties, but its application to reactive water models remains underexplored. Here, we present an extension of the energy-bias aggregation-volume-bias Monte Carlo (EB-AVBMC) method for calculating nucleation free energies and liquid-vapor properties, such as gas density and surface tension, using a three-body reactive force field based on the Vashishta potential functional form [Phys. Rev. B 1990, 41, 12197-12209]. Key modifications include revised acceptance rules that consider the intramolecular energy of the inserted/deleted molecule to prevent high acceptance probabilities that could bias the sampling and constraints to avoid the deletion of dissociated water molecules. These adjustments ensure valid bond topology modifications. We demonstrate the method's applicability by studying water nucleation at 298.15 K, with varying cluster sizes, and showing a free energy consistent with studies from rigid water models. This approach is generalizable to other reactive water force fields, offering a valuable tool for simulating reactive liquid-vapor properties.