Lees-Edwards boundary conditions for translation invariant shear flow: implementation and transport properties

TL;DR

This paper presents a new implementation of Lees-Edwards boundary conditions in MD simulations, enabling detailed study of shear flow effects on soft matter, with validation through transport property measurements.

Contribution

The authors provide the first publicly available implementation of Lees-Edwards boundary conditions in a widely used MD simulation package, ESPResSo.

Findings

Successful implementation of Lees-Edwards boundary conditions in ESPResSo

Comparison of viscosity measurement techniques in shear flow

Observation of anomalous diffusion under shear conditions

Abstract

Molecular dynamics (MD) simulations represent a powerful investigation tool in the field of soft matter. By using shear flows, one can probe the bulk rheology of complex fluids, also beyond the linear response regime, in a way that imitates laboratory experiments. One solution to impose a shear flow in particle-based simulations is the Lees-Edwards technique which ensures that particles experience shear by imposing rules for motion and interactions across the boundary in the direction of the shear plane. Despite their presentation in 1972, a readily available public implementation of Lees-Edwards boundary conditions has been missing from MD simulation codes. In this article, we present our implementation of the Lees-Edwards technique and discuss the relevant technical choices. We used ESPResSo, the extensible simulation package for research on soft matter, for molecular dynamics simulations which can be used as a reference for other implementers. We illustrate our implementation using bulk dissipative particle dynamics fluids, compare different viscosity measurement techniques, and observe the anomalous diffusion in our samples during continuous and oscillatory shear, in good comparison to theoretical estimates.