Applicability of Effective Pair Potentials for Active Brownian Particles

TL;DR

This study evaluates the effectiveness of a proposed scheme to derive effective pair potentials for active Brownian particles, revealing limitations in its applicability and highlighting the non-equilibrium nature of active matter.

Contribution

The paper critically assesses the applicability of an existing effective pair potential scheme to active particles, demonstrating its limited validity and the inherent non-equilibrium behavior.

Findings

Limited parameter range for quantitative agreement

Qualitative differences in virial pressure observed

Active particles exhibit non-equilibrium properties beyond linear response

Abstract

We have performed a case study investigating a recently proposed scheme to obtain an effective pair potential for active Brownian particles [Farage et al., Phys. Rev. E 91, 042310 (2015)]. Applying this scheme to the Lennard-Jones potential, numerical simulations of active Brownian particles are compared to simulations of passive Brownian particles interacting by the effective pair potential. Analyzing the static pair correlations, our results indicate a limited range of activity parameters (speed and orientational correlation time) for which we obtain quantitative, or even qualitative, agreement. Moreover, we find a qualitatively different behavior for the virial pressure even for small propulsion speeds. Combining these findings we conclude that beyond linear response active particles exhibit genuine non-equilibrium properties that cannot be captured by effective pair interaction alone.