Vapor-liquid equilibria of water from first principles: comparison of density functionals and basis sets

Gibbs ensemble Monte Carlo simulations were run with an efficient mixed-basis electronic structure method to explore the phase equilibria of water from first principles using Kohn-Sham density functional theory. The Perdew-Burke-Ernzerhof exchange/correlation density functional gives a higher critical temperature (700 K) and boiling point (480 K) than experiment, although good agreement is found for the saturated liquid densities. A systematic increase in the size of the basis set for the Becke-Lee-Yang-Parr exchange/correlation density functional from a double-zeta to quadruple-zeta split valence leads to further deviations from experiment on the saturated liquid and vapor densities, while the intermediate basis set gives the best results for the heat of vaporization at T = 423 K. Analysis of the liquid structure for all simulations shows changes that can partially be explained by the different densities at a given temperature, and both density functionals show a similar temperature dependence of the liquid structure.