No abstract

This paper reviews recent progress in molecular dynamics simulation of atomic-scale friction measured by an atomic force microscopy. Each section of the review focuses on an individual condition or parameter that affects atomic friction including materials, surfaces, compliance, contact area, normal load, temperature, and velocity. The role each parameter plays is described in the context of both experimental measurements and simulation predictions. In addition, the discussion includes an overview of the research community's current understanding of observed effects, guidelines for implementation of those effects in an atomistic simulation, and suggestions for future research to address open questions. Taken together, this review conveys the message that friction at the atomic scale is affected by many interrelated parameters and that the use of molecular dynamics simulation as a predictive tool can be accomplished only through careful model design. V

In this methods article, we describe application of Prandtl-Tomlinson models and their extensions to interpret dry atomic-scale friction. The goal is to provide a practical overview of how to use these models to study frictional phenomena. We begin with the fundamental equations and build on them step-by-step-from the simple quasistatic one-spring, one-mass model for predicting transitions between friction regimes to the two-dimensional and multi-atom models for describing the effect of contact area. The intention is to bridge the gap between theoretical analysis, numerical implementation, and predicted physical phenomena. In the process, we provide an introductory manual with example computer programs for newcomers to the field, and an illustration of the significant potential for this approach to yield new fundamental understanding of atomic-scale friction.

Molecular dynamics simulations are performed to study the frictional behavior of graphene. It is found that the friction between a diamond tip and graphene decreases with increasing number of graphene layers. This behavior is also affected by the graphene sheet size; specifically, the effect of the number of layers on friction becomes significant only when the modeled graphene sheets exceed a critical length. We further show that the frictional behavior can be directly correlated to the height of near-contact wrinkles that resist sliding. These observations are rationalized in terms of the ability of multiple sheets to act as a single material as they resist wrinkle formation.

No abstract