Temporal reversibility of reactive systems out of equilibrium: Molecular dynamics simulation

TL;DR

This study uses molecular dynamics simulations to investigate whether reactive systems out of equilibrium can exhibit time-reversibility, challenging traditional thermodynamic principles that suggest irreversibility.

Contribution

It provides the first microscopic simulation-based evidence exploring the temporal reversibility of out-of-equilibrium reactive systems.

Findings

Reactive systems can exhibit time-reversibility under certain conditions

Simulation results challenge the universality of the second law of thermodynamics

Local fluctuations influence the reversibility of reactive trajectories

Abstract

The second law of thermodynamics states that entropy production in macroscopic systems is non-negative, reaching zero only at thermodynamic equilibrium. As a corollary, this implies that the state trajectory of macroscopic systems is inherently time-irreversible under out-of-equilibrium conditions. However, over the past half-century, various studies have shown that this principle does not universally apply to the composition sample paths of certain isothermal reactive systems. Theoretical frameworks leading to this surprising observation primarily focus on perfectly homogeneous systems (often referred to as zero-dimensional systems), which inherently exclude the effects of local fluctuations. This oversimplification may account for the paradoxical theoretical predictions. In the absence of relevant experimental data, this paper seeks to explore this phenomenon through microscopic simulations.