Berlin 2015 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 10: Colloids and Complex Liquids II (joint CPP/DY/BP)

BP 10.13: Vortrag

Montag, 16. März 2015, 18:15–18:30, C 130

New relaxation process for water in electric fields — •Zoran Miličević¹, David M. Smith^2,3, and Ana-Sunčana Smith^1,3 — ¹Institut für Theoretische Physik and Cluster of Excellence: Engineering of Advanced Materials, FAU Erlangen-Nürnberg, Erlangen, Germany — ²Computer Chemie Centrum, FAU Erlangen-Nürnberg, Erlangen, Germany — ³Ruđer Bošković Institute, Zagreb, Croatia

Despite a heavily increasing number of electrochemical applications, theoretical and experimental studies of solvent shear properties in the presence of electric fields are almost non-existent. Here we study the shear viscosity of water by performing extensive MD simulations using the GROMACS software package as a function of the electric field strength which breaks the otherwise isotropic nature of the solvent. The shear viscosity is related to the autocorrelation function (ACF) of the off-diagonal elements of the pressure tensor by the Green-Kubo relation. The value of the shear viscosity is determined from the plateau value of the time integral of the ACF or, alternatively, by exploiting the Kohlrausch fit curve of the ACF using a uniform 2-step (fast plus slow) relaxation function. Apart from the fact that the two approaches show an excellent agreement, we find that the field decreases the component of the shear viscosity perpendicular to itself and increases the components which are parallel. Importantly, the field induces an additional slow relaxation process (decoupled from the fast relaxation) only in the parallel direction, increasing by about tenfold the total relaxation time with respect to the perpendicular direction. Furthermore, the overall water shear viscosity increases slightly with the field strength.