Structure and polarization properties of water: Molecular dynamics with a nonadditive intermolecular potential

The temperature and density dependence of the structure and polarization properties of bulk water were systematically investigated using the ab initio MCYna potential, which includes nonadditive contributions to intermolecular interactions. Molecular dynamics simulations were conducted for isochores of 1, 0.8, and 0.6 g/cm3 and temperatures from 278 to 750 K. Special attention was paid to the structural change of water in the range from the normal boiling point to supercritical temperatures. At temperatures below the normal boiling temperature, water exhibits a tetrahedral structure along the 0.8 and 0.6 g/cm3 isochores. A significant collapse of the hydrogen bonding network was observed at temperatures of 450, 550, and 650 K. The MCYna potential was able to successfully reproduce the experimental dielectric constant. The dielectric constant and average dipole moments decrease with increasing temperature and decreasing density due to weakened polarization. A comparison is also made with SPC-based models.