Application of integral equation theories to predict the structure, thermodynamics, and phase-behavior of water

We analyze the predictive capabilities of the site?site Ornstein?Zernike equation and the Chandler? Silbey?Ladanyi equations for various potential models of water. Specifically, we solve ~i! the site?site Ornstein?Zernike equation with the hypernetted-chain closure, and ~ii! the Chandler? Silbey?Ladanyi equations with the hypernetted-chain closure as well as with the zeroth-order bridge functions, and compare their predictions of the structure, thermodynamics, and phase behavior of water with those obtained from computer simulations and experimental measurements. The predictions of the various site?site pair correlation functions of water for both integral equations are comparable. However, the Chandler?Silbey?Ladanyi equations seem to better predict the structure of the fluid beyond the first coordination shell. In addition, the Chandler?Silbey?Ladanyi equations provide better estimates of the thermodynamic properties of water as compared to those of the site?site Ornstein?Zernike equation, when the results are compared with those of computer simulations. We also predict the liquid?vapor coexistence curve and the vapor pressure of water using both integral equations. The Chandler?Silbey?Ladanyi equations predict higher densities of the coexisting liquid and vapor branches as compared to those predicted by the site?site Ornstein? Zernike equation. The predictions of the Chandler?Silbey?Ladanyi equations for the liquid branch are found to be in better agreement with the computer simulations data, while the site?site Ornstein?Zernike equation is found to work better for the vapor branch. The vapor pressure predictions of the site?site Ornstein?Zernike equation are found to be in good agreement with the experimental values, while the Chandler?Silbey?Ladanyi equations are found to give slightly higher predictions of the vapor pressure.