title: Dynamical behavior near a liquid-liquid phase transition in simulations of supercooled water.
abstract: We examine the behavior of the diffusion coefficient of the ST2 model of water over a broad region of the phase diagram via molecular dynamics simulations. The ST2 model has an accessible liquid-liquid transition between low-density and high-density phases, making the model an ideal candidate to explore the impacts of the liquid-liquid transition on dynamics. We locate characteristic dynamical loci in the phase diagram and compare them with the previously investigated thermodynamic loci. The low-density liquid phase shows a crossover from non-Arrhenius to Arrhenius behavior, signaling the onset of a crossover from fragile-to-strong behavior. We explain this crossover in terms of the asymptotic approach of the low-density liquid to a random tetrahedral network and show that the temperature dependence of the diffusion coefficient over a wide temperature range can be simply related to the concentration of defects in the network. Our findings thus confirm that the low-density phase of ST2 water is a well-defined metastable liquid.
authors.affiliation: Department of Physics, St. Francis Xavier University, Antigonish, Nova Scotia B2G 2W5, Canada. ppoole@stfx.ca
authors.forename: Peter H
authors.initials: PH
authors.lastname: Poole
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Becker
authors.forename: Francesco
authors.initials: F
authors.lastname: Sciortino
authors.forename: Francis W
authors.initials: FW
authors.lastname: Starr