title: Structure and dynamics of high- and low-density water molecules in the liquid and supercooled regimes.
abstract: By combining the local structure index with potential energy minimisations we study the local environment of the water molecules for a couple of water models, TIP5P-Ew and SPC/E, in order to characterise low- and high-density "species". Both models show a similar behaviour within the supercooled regime, with two clearly distinguishable populations of unstructured and structured molecules, the fraction of the latter increasing with supercooling. Additionally, for TIP5P-Ew, we find that the structured component vanishes quickly at the normal liquid regime (above the melting temperature). Thus, while SPC/E provides a fraction of structured molecules similar to that found in X-ray experiments, we show that TIP5P-Ew underestimates such value. Moreover, unlike SPC/E, we demonstrate that TIP5P-Ew does not follow the linear dependence of the logarithm of the structured fraction with inverse temperature, as predicted by the two-order parameter model. Finally, we link structure to dynamics by showing that there exists a strong correlation between structural fluctuation and dynamics in the supercooled state with spatial correlations in both static and dynamic quantities.
authors.affiliation: Sección Fisicoquímica - INQUISUR and Departamento de Química, Universidad Nacional del Sur, Avenida Alem 1253, 8000-Bahía, Blanca, Argentina.
authors.forename: Joan Manuel
authors.initials: JM
authors.lastname: Montes de Oca
authors.affiliation: Sección Fisicoquímica - INQUISUR and Departamento de Química, Universidad Nacional del Sur, Avenida Alem 1253, 8000-Bahía, Blanca, Argentina. rodriguezfris@uns.edu.ar.
authors.forename: J Ariel
authors.initials: JA
authors.lastname: Rodriguez Fris
authors.affiliation: Sección Fisicoquímica - INQUISUR and Departamento de Química, Universidad Nacional del Sur, Avenida Alem 1253, 8000-Bahía, Blanca, Argentina.
authors.forename: Sebastián R
authors.initials: SR
authors.lastname: Accordino
authors.affiliation: Department of Biological Engineering, Northwestern University, Evanston, IL, USA.
authors.forename: David C
authors.initials: DC
authors.lastname: Malaspina
authors.affiliation: Sección Fisicoquímica - INQUISUR and Departamento de Química, Universidad Nacional del Sur, Avenida Alem 1253, 8000-Bahía, Blanca, Argentina.
authors.forename: Gustavo A
authors.initials: GA
authors.lastname: Appignanesi
mesh_terms: D008956:Models, Chemical; D013696:Temperature; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water
keywords: Flowing Matter: Liquids and Complex Fluids