Communication: On the origin of the non-Arrhenius behavior in water reorientation dynamicsReport as inadecuate




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* Corresponding author 1 PASTEUR - Processus d-Activation Sélective par Transfert d-Energie Uni-électronique ou Radiatif 2 Dpt of Chemistry New York

Abstract : We combine molecular dynamics simulations and analytic modeling to determine the origin of the non-Arrhenius temperature dependence of liquid water-s reorientation and hydrogen-bond dynamics between 235 K and 350 K. We present a quantitative model connecting hydrogen-bond exchange dynamics to local structural fluctuations, measured by the asphericity of Voronoi cells associated with each water molecule. For a fixed local structure the regular Arrhenius behavior is recovered, and the global anomalous temperature dependence is demonstrated to essentially result from a continuous shift in the unimodal structure distribution upon cooling. The non-Arrhenius behavior can thus be explained without invoking an equilibrium between distinct structures. In addition, the large width of the homogeneous structural distribution is shown to cause a growing dynamical heterogeneity and a non-exponential relaxation at low temperature.





Author: Guillaume Stirnemann - Damien Laage -

Source: https://hal.archives-ouvertes.fr/



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