title: Spatially inhomogeneous bimodal inherent structure of simulated liquid water.
abstract: In the supercooled regime at elevated pressure two forms of liquid water, high-density (HDL) and low-density (LDL), have been proposed to be separated by a coexistence line ending at a critical point, but a connection to water at ambient conditions has been lacking. Here we perform large-scale molecular dynamics simulations and demonstrate that the underlying potential energy surface gives a strictly bimodal characterization of the molecules at all temperatures and pressures, including the biologically and technologically important ambient regime, as spatially inhomogeneous either LDL- or HDL-like with a 3 : 1 predominance for HDL under ambient conditions. The Widom line in the supercooled regime, where maximal structural fluctuations take place, coincides with a 1 : 1 distribution. Although our results are based on molecular dynamics force-field simulations the close agreement with recent analyses of experimental X-ray spectroscopy and scattering data indicates a unified description also of real liquid water covering supercooled to ambient conditions.
authors.affiliation: Department of Physics, AlbaNova, Stockholm University, S-106 91 Stockholm, Sweden.
authors.forename: K T
authors.initials: KT
authors.lastname: Wikfeldt
authors.forename: A
authors.initials: A
authors.lastname: Nilsson
authors.forename: L G M
authors.initials: LG
authors.lastname: Pettersson