Vapor-liquid equilibrium of water with the MB-pol many-body potential

MC Muniz and TE Gartner and M Riera and C Knight and S Yue and F Paesani and AZ Panagiotopoulos, JOURNAL OF CHEMICAL PHYSICS, 154, 211103 (2021).

DOI: 10.1063/5.0050068

Among the many existing molecular models of water, the MB-pol many-body potential has emerged as a remarkably accurate model, capable of reproducing thermodynamic, structural, and dynamic properties across water's solid, liquid, and vapor phases. In this work, we assessed the performance of MB-pol with respect to an important set of properties related to vapor-liquid coexistence and interfacial behavior. Through direct coexistence classical molecular dynamics simulations at temperatures of 400 K < T < 600 K, we calculated properties such as equilibrium coexistence densities, vapor-liquid interfacial tension, vapor pressure, and enthalpy of vaporization and compared the MB-pol results to experimental data. We also compared rigid vs fully flexible variants of the MB-pol model and evaluated system size effects for the properties studied. We found that the MB-pol model predictions are in good agreement with experimental data, even for temperatures approaching the vapor-liquid critical point; this agreement was largely insensitive to system sizes or the rigid vs flexible treatment of the intramolecular degrees of freedom. These results attest to the chemical accuracy of MB- pol and its high degree of transferability, thus enabling MB-pol's application across a large swath of water's phase diagram.

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