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 6 00 K, which is close to the freezing point, no appreciable molecular dissoc iation is observed in the simulations. However, the structure of water is s ubstantially altered from that at ambient conditions. The liquid exhibits a much larger coordination of oxygen atoms, an essential weakening of hydrog en bonding, and sizable changes in the density of electronic states close t o the Fermi level. Our results provide new structural data for direct compa rison with future experiments.