Phase coexistence properties for the polarizable point charge model of water and the effects of applied electric field

Extensive efforts are currently devoted to the development of water models for computer simulations that explicitly incorporate molecular polarizability. Liquid-vapor coexistence properties for the polarizable point charge (PPC) model of water are examined in this contribution with the aid of molecular dynamics calculations. An accurate analytical equation of state for the high-temperature states of the PPC model is presented, including its critical region. The liquid-vapor coexistence curve and the critical point parameters for the PPC water are extracted from its equation of state. The critical temperature, pressure, and density for the PPC water are found to be within 10% of their experimental values and its critical compression factor is within 2%. The effect of applying an external electric field to the system on the coexistence properties is investigated. A shift of the critical point of water to higher temperature and pressure is observed, a result similar to that of the introduction of an electrolyte to water. A large applied electric field is capable of inducing phase separation of a subcritical fluid on the time scale of a typical simulation run. (C) 1999 American Institute of Physics. [S0021-9606(99)51542-0].