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

TL;DR

This study evaluates the MB-pol many-body potential's accuracy in predicting vapor-liquid equilibrium properties of water, demonstrating its high transferability and agreement with experimental data across a range of temperatures.

Contribution

The paper provides a comprehensive assessment of MB-pol's performance in vapor-liquid coexistence and interfacial properties, confirming its accuracy and transferability.

Findings

MB-pol accurately predicts vapor-liquid coexistence properties.

Results are consistent across system sizes and molecular flexibility variants.

MB-pol remains accurate near the vapor-liquid critical point.

Abstract

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 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 size 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.