Long-time self-diffusion of Brownian Gaussian-core particles

TL;DR

This study uses Brownian dynamics simulations to analyze the long-time self-diffusion behavior of Gaussian-core particles, revealing non-monotonic diffusion trends and weak translation-rotation coupling in Gaussian rods.

Contribution

It provides the first detailed simulation-based analysis of long-time diffusion for Gaussian-core particles, including both spherical and rod-like shapes, and compares results with theoretical predictions.

Findings

Translational self-diffusion shows non-monotonic behavior with density.

Long-time orientational diffusion remains close to short-time values for Gaussian rods.

Microscopic theory qualitatively explains translational diffusion trends.

Abstract

Using extensive Brownian dynamics computer simulations, the long-time self-diffusion coefficient is calculated for Gaussian-core particles as a function of the number density. Both spherical and rod-like particles interacting via Gaussian segments ar$ For increasing concentration we find that the translational self-diffusion behaves non-monotonically reflecting the structural reentrance effect in the equilibrium phase diagram. Both in the limits of zero and infinite concentration, it approaches its short-time value. The microscopic Medina-Noyola theory qualitatively accounts for the translational long-time diffusion. The long-time orientational diffusion coefficient for Gaussian rods, on the other hand, remains very close to its short-time counterpart for any density. Some implications of the weak translation-rotation coupling for ultrasoft rods are discussed.