Slip and Stress From Low Strain-Rate Nonequilibrium Molecular Dynamics: The Transient-Time Correlation Function Technique

TL;DR

This paper introduces the transient-time correlation function (TTCF) technique for accurately computing shear stress and slip velocity in atomistic fluids under low shear rates using nonequilibrium molecular dynamics, enhancing precision over traditional methods.

Contribution

The paper derives a new TTCF formalism for inhomogeneous confined fluids and demonstrates its effectiveness in low shear rate simulations, improving accuracy in rheological studies.

Findings

TTCF significantly improves accuracy at low shear rates.

TTCF is suitable for studying tribology and rheology of confined fluids.

Method outperforms direct averaging in molecular dynamics simulations.

Abstract

We derive the transient-time correlation function (TTCF) expression for the computation of phase variables of inhomogenous confined atomistic fluids undergoing boundary-driven planar shear (Couette) flow at constant pressure. Using nonequilibrium molecular dynamics simulations, we then apply the TTCF formalism to the computation of the shear stress and the slip velocity for atomistic fluids at realistic low shear rates, in systems under constant pressure and constant volume. We show that, compared to direct averaging of multiple trajectories, the TTCF method dramatically improves the accuracy of the results at low shear rates, and that it is suitable to investigate the tribology and rheology of atomistically detailed confined fluids at realistic flow rates.