With recent advances in molecular simulation analysis techniques such as multistate reweighting and analytic mapping of configurational ensembles, it is becoming possible to reconstruct the entire thermodynamic profile of molecular fluids as a function of temperature and pressure over large multidimensional model parameter spaces using a reasonably small amount of computational power.In this study, we use such statistical mechanical analysis techniques to characterize the liquid state thermodynamics of 3- and 4-site rigid water models as a function of temperature and pressure over a six dimensional parameter space: charge, oxygen Lennard-Jones sigma and epsilon, OH distance, HH distance, and charge offset from Lennard-Jones site center. Using approximate analytical models to roughly screen this large parameter space, we identify regions in this parameter space that are 'water-like' and characterize their thermodynamics with high precision using both direct simulation and reweighting identities. This allows us to identify families of models that equally well describe the thermodynamics of water.We also explore the utility of comparing water models to experiment using the residual Gibbs free energy itself as a function of temperature and pressure, which can be reconstructed with high precision from experimental properties, rather than using thermodynamic properties such as enthapies, densities, heat capacities, and compressibilities, which are all derivatives of the Gibbs free energy.

Exploring thermodynamics over water model parameter space

247th National Meeting (2014)

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