8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P2.72Tue 611:23-14:00Solid/liquid and liquid/vapor equilibria for common watermodelsRyuji Sakamaki, 1 Amadeu Sum, 2 Tetsu Narumi, 3 and Kenji Yasuoka 11 Keio University, 3-14-1 Hiyoshi, Kohokuku, 223-8522, Yokohama, Japan2 Colorado School of Mines, Golden, CO, United States of America3 The university of electro-communications, Chofushi, JapanIt is well acknowledged that the equilibrium properties vary with potential model in classicalmolecular simulations. In this work, the liquid/vapor and solid/liquid coexistence properties forcommon water models were examined by using molecular dynamics simulations. The liquid/vaporsystem was simulated in the NV T ensemble. The solid/liquid system was simulated in the NPHensemble, and repeated until the temperature reaches the equilibrium temperature. We found thatthe TIP4P/2005 and TIP4P-i models reproduce the experimental liquid saturation density and surfacetension in a wide range of temperature conditions. The reduced temperature of T/Tc givesconsistent equilibrium densities and pressures. The melting temperatures at 1 bar for newly developedmodels were obtained. We also found that much better agreement with experiment isprovided by the TIP5P/Ew, TIP4PQ/2005 and TIP4P-i models. It can be concluded the TIP4P-iis the most successful potential model of water in terms of the equilibrium properties. We alsoexamined the modified nonpolarizable model which has the same Lennard-Jones parameters as theTIP4P-FQ model but uses an adjustable molecular dipole moment. This modified model with amolecular dipole moment of 2.72 Debye gives the best estimate of experimental surface tension,but its melting temperature is about 110 K lower than the experimental studies.72