Sensitivity analysis of water thermodynamics

Abstract

Sensitivity analysis in various thermodynamic properties of liquid water is performed based on two flexible three-site models. It is found that the determinative factors for the Helmholtz free energy and the system internal energy are the gas-phase O–H bond length and the Lennard-Jones radius. The Lennard-Jones radius also plays a predominating role in evaluating the thermodynamic pressure. On the other hand, the statistical entropy, the heat capacity at constant volume, and the thermal pressure coefficient are mainly controlled by the parameters relating to the O–H bond stretching. In addition, the Kirkwood Gk factor is quite sensitive to the cutoff radius in the reaction field geometry. This study helps understand the thermodynamics in liquid water and provides useful hints for further improving the current water models.