Calculating shear viscosity with confined non-equilibrium molecular dynamics: a case study on hematite - PAO-2 lubricant

The behaviour of confined lubricants at the atomic scale as affected by the interactions at the surface-lubricant interface is relevant in a range of technological applications in areas such as the automotive industry. In this paper, by performing fully atomistic molecular dynamics, we investigate t...

Full description

Saved in:
Bibliographic Details
Published in:RSC advances 2023-11, Vol.13 (48), p.33994-342
Main Authors: Mathas, Dimitrios, Sarpa, Davide, Holweger, Walter, Wolf, Marcus, Bohnert, Christof, Bakolas, Vasilios, Procelewska, Joanna, Franke, Joerg, Rödel, Philipp, Skylaris, Chris-Kriton
Format: Article
Language:English
Subjects:
Atomic interactions
Automobile industry
Film thickness
Hematite
Iron oxides
Lubricants & lubrication
Molecular dynamics
Shear flow
Shear viscosity
Simulation
Viscosity
Citations: Items that this one cites
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The behaviour of confined lubricants at the atomic scale as affected by the interactions at the surface-lubricant interface is relevant in a range of technological applications in areas such as the automotive industry. In this paper, by performing fully atomistic molecular dynamics, we investigate the regime where the viscosity starts to deviate from the bulk behaviour, a topic of great practical and scientific relevance. The simulations consist of setting up a shear flow by confining the lubricant between iron oxide surfaces. By using confined Non-Equilibrium Molecular Dynamics (NEMD) simulations at a pressure range of 0.1-1.0 GPa at 100 °C, we demonstrate that the film thickness of the fluid affects the behaviour of viscosity. We find that by increasing the number of lubricant molecules, we approach the viscosity value of the bulk fluid derived from previously published NEMD simulations for the same system. These changes in viscosity occurred at film thicknesses ranging from 10.12 to 55.93 Å. The viscosity deviations at different pressures between the system with the greatest number of lubricant molecules and the bulk simulations varied from −16% to 41%. The choice of the utilized force field for treating the atomic interactions was also investigated. Atomistic simulations show for the first time how the variation of a lubricant's film thickness affects viscosity and at what point it eventually becomes comparable with the bulk simulation of a lubricant, at different pressures and shear regimes.
ISSN:2046-2069
2046-2069
DOI:10.1039/d3ra06929j