Multiscale treatment of thin-film lubrication

A multiscale technique that combines an atomistic description of the interfacial (near) region with a coarse-grained (continuum) description of the far regions of the solid substrates is proposed. The new hybrid technique, which represents an advance over a previously proposed dynamically-constrained hybrid atomistic-coarse-grained treatment (Wu, et al., J. Chem. Phys. 120, 6744, 2004), is applied to a two-dimensional model tribological system comprising planar substrates sandwiching a monolayer film. Shear-stress profiles (shear stress versus strain) computed by the new hybrid technique are in excellent agreement with "exact" profiles (i.e., those computed treating the whole system at the atomic scale)

Hybrid Atomistic-Coarse-Grained Treatment of Thin-Film Lubrication II

A new hybrid atomistic-coarse-grained ~HACG! treatment of reversible processes in multiple-scale systems involving fluid-solid interfaces was tested through isothermal-isobaric Monte Carlo simulations of the quasistatic shearing of a model two-dimensional lubricated contact comprising two planar Lennard-Jones solid substrates that sandwich a softer Lennard-Jones film. Shear-stress profiles ~plots of shear stress Tyx versus lateral displacement of the substrates! obtained by the HACG technique, which combines an atomistic description of the interfacial region with a continuum description of regions well removed from the interface, are compared with ‘‘exact’’ profiles ~obtained by treating the whole system at the atomic scale! for a selection of thermodynamic states that correspond to systematic variations of temperature, load ~normal stress!, film-substrate coupling strength, and film thickness. The HACG profiles are in excellent agreement overall with the exact ones. The HACG scheme provides a reliable description of quasistatic shearing under a wide range of conditions. It is demonstrated that the elastic response of the remote regions of the substrates can have a significant impact on the static friction profile ~plot of maximum magnitude of Tyx versus load

An extension of the Quasicontinuum Treatment of Multiscale Solid Systems to Nonzero Temperature

Covering the solid lattice with a finite-element mesh produces a coarse-grained system of mesh nodes as pseudoatoms interacting through an effective potential energy that depends implicitly on the thermodynamic state. Use of the pseudoatomic Hamiltonian in a Monte Carlo simulation of the two-dimensional Lennard-Jones crystal yields equilibrium thermomechanical properties (e.g., isotropic stress) in excellent agreement with ``exact'' fully atomistic results

Multiscale Treatment of Thin-Film Lubrication

A multiscale technique that combines an atomistic description of the interfacial (near) region with a coarse-grained (continuum) description of the far regions of the solid substrates is proposed. The new hybrid technique, which represents an advance over a previously proposed dynamically-constrained hybrid atomistic-coarse-grained treatment (Wu et al.J. Chem. Phys., 120, 6744, 2004), is applied to a two-dimensional model tribological system comprising planar substrates sandwiching a monolayer film. Shear–stress profiles (shear stress versus strain) computed by the new hybrid technique are in excellent agreement with “exact” profiles (i.e. those computed treating the whole system at the atomic scale)