Please use this identifier to cite or link to this item:
Title: TTCF4LAMMPS: A toolkit for simulation of the non-equilibrium behaviour of molecular fluids at experimentally accessible shear rates
Authors: Maffioli, L
Ewen, JP
Smith, ER
Varghese, S
Daivis, PJ
Dini, D
Todd, BD
Keywords: shear rate;viscosity;shear stress;slip;transient time correlation function (TTCF);nonequilibrium molecular dynamics (NEMD);friction;tribology
Issue Date: 15-Apr-2024
Publisher: Elsevier
Citation: Maffioli, L. (2024) 'TTCF4LAMMPS: A toolkit for simulation of the non-equilibrium behaviour of molecular fluids at experimentally accessible shear rates', Computer Physics Communications, 300, 109205, pp. 1 - 12. doi: 10.1016/j.cpc.2024.109205.
Abstract: We present TTCF4LAMMPS, a toolkit for performing non-equilibrium molecular dynamics (NEMD) simulations to study the fluid behaviour at low shear rates using the LAMMPS software. By combining direct NEMD simulations and the transient-time correlation function (TTCF) technique, we study the fluid response to shear rates spanning 15 orders of magnitude. We present two examples for simple monatomic systems: one consisting of a bulk liquid and another with a liquid layer confined between two solid walls. The small bulk system is suitable for testing on personal computers, while the larger confined system requires high-performance computing (HPC) resources. We demonstrate that the TTCF formalism can successfully detect the system response for arbitrarily weak external fields. We provide a brief mathematical explanation for this feature. Although we showcase the method for simple monatomic systems, TTCF can be readily extended to study more complex molecular fluids. Moreover, in addition to shear flows, the method can be extended to investigate elongational or mixed flows as well as thermal or electric fields. The high computational cost needed for the method is offset by the two following benefits: i) the cost is independent of the magnitude of the external field, and ii) the simulations can be made highly efficient on HPC architectures by exploiting the parallel design of the algorithm. We expect the toolkit to be useful for computational researchers striving to study the nonequilibrium behaviour of fluids under experimentally-accessible conditions.
Description: Program summary: Program title: TTCF4LAMMPS CPC Library link to program files: Developer's repository link: Licensing provisions: GNU General Public License 3 Programming language: Python 3 Nature of problem: Measuring the nonequilibrium behaviour of bulk and confined fluids under experimentally accessible strain rates in non-equilibrium molecular dynamics (NEMD) simulations. Solution method: Creating a Python-based code that utilises the transient-time correlation function method and the LAMMPS software to enable the bulk fluid properties (e.g. viscosity) and confined fluid interfacial properties (e.g. shear stress and slip velocity) to be computed at low shear rates with NEMD.
Data availability: All data used in this work are freely reproducible using the program provided. The source files are also available at the link
ISSN: 0010-4655
Other Identifiers: ORCiD: Luca Maffioli
ORCiD: Edward R. Smith
Appears in Collections:Dept of Mechanical and Aerospace Engineering Research Papers

Files in This Item:
File Description SizeFormat 
FullText.pdfCopyright © 2024 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license ( kBAdobe PDFView/Open

This item is licensed under a Creative Commons License Creative Commons