Water under pressure

Water under pressure is investigated by first principles molecular dynamics, with a focus on the changes in hydrogen bonding and the oxygen network in the nondissociative regime. At a pressure of 10 GPa and a temperature of 600 K, which is close to the freezing point, no appreciable molecular dissociation is observed in the simulations. However, the structure of water is substantially altered from that at ambient conditions. The liquid exhibits a much larger coordination of oxygen atoms, an essential weakening of hydrogen bonding, and sizable changes in the density of electronic states close to the Fermi level. Our results provide new structural data for direct comparison with future experiments.