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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 17: Modeling and Simulation of Soft Matter I

CPP 17.2: Vortrag

Dienstag, 18. März 2025, 10:00–10:15, H38

Coupled self and collective dynamics in highly charged colloidal Yukawa-systems — •Daniel Weidig and Joachim Wagner — University of Rostock, Rostock, Germany

We investigate binary mixtures of highly charged colloidal particles employing Brownian dynamics simulations. In mixtures of identically charged, but differently sized particles solely the Stokes-Einstein diffusion coefficients differ, while the interactions are practically size-independent. Due to these identical interactions the static structure of all species are identical and independent on dynamical properties of the particles, as observed in partial static pair correlation functions. A dynamical coupling of both self and collective motion is observed in these systems. The long-time self-diffusion coefficient of a larger species is enhanced by the presence of a smaller, more mobile species and vice versa. Similar coupling effects are as well observed in the initial correlation decay of partial, distinct intermediate scattering functions, quantified by relaxation rates and stretching exponents of stretched exponentials. For all the here mentioned parameters, in the limit of strongly electrostatically coupled colloidal systems in first approximation linear dependencies on the size-ratio and reduced number density are observed. Despite we investigated highly dilute colloidal suspensions, where normally hydrodynamic interactions are neglectable, we found especially in binary mixtures an enhancement of the self and collective diffusion coefficients due to hydrodynamic interactions. Contrary, in one-component systems, hydrodynamic interactions do not have significant influence on time-dependent diffusion coefficients.

Keywords: Brownian dynamics simulation; Colloidal suspensions; Collective motion; Hydrodynamic interaction