RT Journal Article
T1 Viscosity and self-diffusion of supercooled and stretched water from molecular dynamics simulations
A1 Montero de Hijes, Pablo
A1 Sanz García, Eduardo
A1 Joly, Laurent
A1 Valeriani, Chantal
A1 Caupin, Frederic
AB Among the numerous anomalies of water, the acceleration of dynamics under pressure is particularly puzzling. Whereas the diffusivity anomaly observed in experiments has been reproduced in several computer studies, the parallel viscosity anomaly has received less attention. Here we simulate viscosity and the self-diffusion coefficient of the TIP4P/2005 water model over a broad temperature and pressure range. We reproduce the experimental behavior and find additional anomalies at negative pressure. The anomalous effect of pressure on dynamic properties becomes more pronounced upon cooling, reaching two orders of magnitude for viscosity at 220 K. We analyze our results with a dynamic extension of a thermodynamic two-state model, an approach which has proved successful in describing experimental data. Water is regarded as a mixture of interconverting species with contrasting dynamic behaviors, one being strong (Arrhenius) and the other fragile (non-Arrhenius). The dynamic parameters of the two-state models are remarkably close between experiment and simulations. The larger pressure range accessible to simulations suggests a modification of the dynamic two-state model, which in turn also improves the agreement with experimental data. Furthermore, our simulations demonstrate the decoupling between viscosity eta and self-diffusion coefficient D as a function of temperature T. The Stokes-Einstein relation, which predicts a constant D eta/T, is violated when T is lowered, in connection with the Widom line defined by an equal fraction of the two interconverting species. These results provide a unifying picture of thermodynamics and dynamics in water and call for experiments at negative pressure. Published by AIP Publishing.
PB Amer Inst Physics
SN 0021-9606
YR 2018
FD 2018-09-07
LK https://hdl.handle.net/20.500.14352/13080
UL https://hdl.handle.net/20.500.14352/13080
LA eng
NO © 2018 Author(s). P.M.H., E.S., and C.V. have been funded by Grant Nos. FIS2013/43209-P, FIS2016-78117-P, and FIS2016-78847-P of the MEC and the UCM/Santander Nos. 910570 and PR26/16-10B-2. P.M.H. acknowledges financial support from a FPI Ph.D. fellowship. L.J. acknowledges support from Institut Universitaire de France. This work was partially supported by CNRS (France) through a PICS program.
NO Ministerio de Educación y Ciencia (MEC)
NO Universidad Complutense de Madrid/Banco de Santander
NO FPI Ph.D. fellowship
NO Institut Universitaire de France
NO CNRS (France) through a PICS program
DS Docta Complutense
RD 29 abr 2024