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DY: Fachverband Dynamik und Statistische Physik

DY 59: Brownian Motion and Anomalous Diffusion

DY 59.13: Talk

Friday, March 22, 2024, 12:45–13:00, BH-N 334

Coupled long-time dynamics in binary mixtures of colloidal Yukawa-systems — •Daniel Weidig and Joachim Wagner — Institut für Chemie, Universität Rostock, 18051 Rostock, Germany

We investigate structure and dynamics of binary mixtures consisting of particles interacting via a screened Coulomb potential. In mixtures of equally charged, but differently sized particles, the partial correlation functions g_AA(r)=g_AB(r)=g_BB(r) and thus partial static structure factors are identical due to identical time-averaged interactions between all present species. Different particle sizes, however, yield different Stokes-Einstein diffusion coefficients with σ_A/σ_B=D_0,B/D_0,A. Mediated by electrostatic interactions, different mobilities of the species influence the long-time diffusion: In presence of a smaller species, the long-time diffusion of the larger species is accelerated and vice versa as visible both in self- and collective dynamics. A nearly universal dependence of the relative acceleration or deceleration of long-time self-diffusion coefficients in mixtures on the product of size-ratio σ_A/σ_B of the larger to the smaller species and number-density ratio ϱ_i^*/ϱ_i is observed. Here, ϱ_i^* denotes the number density of species i in a suspension containing only species i and ϱ_i the number density of species i in a mixture. The magnitude of the relative acceleration or deceleration depends in first approximation on the electrostatic interaction at the maximum r_max of the pair correlation functions g_ij(r).

Keywords: Long-time Dynamics; Brownian Dynamics Simulation; Colloidal Suspensions; Self Dynamics; Collective Dynamics