Dynamics of friction: superlubric state

Shinjo, Kazumasa; Hirano, Motohisa

doi:10.1016/0167-2584(93)90720-4

Cited by 36 publications

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“…The high-velocity friction reduction plateau of Fig. 4c, where thermal hopping is negligible, then represents a direct observation of structurally-induced lubricity or "superlubricity" [4][5][6][7] . This interpretation is consistent with the observation that in this regime, the ions pass the barrier one at a time ( Fig.…”

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confidence: 92%

Velocity tuning of friction with two trapped atoms

et al. 2015

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Friction is the basic, ubiquitous mechanical interaction between two surfaces that results in resistance to motion and energy dissipation. In spite of its technological and economic significance, our ability to control friction remains modest, and our understanding of the microscopic processes incomplete 1-3 . At the atomic scale, mismatch between the two contacting crystal lattices can lead to a reduction of stick-slip friction (structural lubricity) 4-7 , while thermally activated atomic motion can give rise to a complex velocity dependence 8-14 , and nearly vanishing friction at sufficiently low velocities (thermal lubricity) 10,13 . Atomic force microscopy has provided a wealth of experimental results 6-9,14-19 , but limitations in the dynamic range, time resolution, and control at the single-atom level have hampered a full quantitative description from first principles 3 . Here, using an ion-crystal friction emulator with single-atom, single substrate-site spatial resolution and single-slip temporal resolution 5,20 , we measure the friction force over nearly five orders of magnitude in velocity, and contiguously observe four distinct regimes, while controlling temperature and dissipation. We elucidate the interplay between thermal and structural lubricity in a system of two coupled atoms, and provide a simple explanation in terms of the Peierls-Nabarro potential 21 . This extensive control at the atomic scale paves the way for fundamental studies of the interaction of many-atom surfaces, as for example in the Frenkel-Kontorova model 21 , and possibly into the quantum regime 22 .

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confidence: 92%

Velocity tuning of friction with two trapped atoms

et al. 2015

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“…For a purely incommensurate infinite contact, theoretical arguments suggest that static friction should vanish [2]. However, very low friction has been measured also for finite incommensurate contacts at very low velocities [3,4] and this effect has been called superlubricity [5][6][7]. The atomic force microscope (AFM) study [3,4] found that the sliding of graphite flakes on graphite can occur with very low friction, depending strongly on the relative orientation.…”

Section: Introductionmentioning

confidence: 99%

Stability of Low-Friction Surface Sliding of Nanocrystals with Rectangular Symmetry and Application to W on NaF(001)

Wijn

Fasolino

2010

Tribol Lett

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We investigate the stability of low-friction sliding of nanocrystal with rectangular atomic arrangement on rectangular lattices, for which analytical results can be obtained. We find that several incommensurate periodic orbits exist and are stable against thermal fluctuations and other perturbations. As incommensurate orientations lead to low corrugation, and therefore low friction, such incommensurate periodic orbits are interesting for the study of nanotribology. The analytical results compare very well with simulations of W nanocrystals on NaF(001). The geometry and high typical corrugation of substrates with square lattices increase the robustness when compared to typical hexagonal lattices, such as graphite.

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“…In all cases the interactions were too weak to produce static friction. Shinjo and Hirano (1993) extended this line of work to dynamical simulations of sliding. They first considered the undamped Frenkel-Kontorova model with ideal springs between atoms.…”

Section: A Effect Of Commensurabilitymentioning

confidence: 99%

Computer Simulations of Friction, Lubrication, and Wear

Robbins¹,

Müser²

2000

Mechanics &Amp; Materials Science

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Computer simulations have played an important role in understanding tribological processes. They allow controlled numerical "experiments" where the geometry, sliding conditions and interactions between atoms can be varied at will to explore their effect on friction, lubrication, and wear. Unlike laboratory experiments, computer simulations enable scientists to follow and analyze the full dynamics of all atoms. Moreover, theorists have no other general approach to analyze processes like friction and wear. There is no known principle like minimization of free energy that determines the steady state of non-equilibrium systems. Even if there was, simulations would be needed to address the complex systems of interest, just as in many equilibrium problems.Tremendous advances in computing hardware and methodology have dramatically increased the ability of theorists to simulate tribological processes. This has led to an explosion in the number of computational studies over the last decade, and allowed increasingly sophisticated modeling of sliding contacts. Although it is not yet possible to treat all the length scales and time scales that enter the friction coefficient of engineering materials, computer simulations have revealed a great deal of information about the microscopic origins of static and kinetic friction, the behavior of boundary lubricants, and the interplay between molecular geometry and tribological properties. These results provide valuable input to more traditional macroscopic calculations. Given the rapid pace of developments, simulations can be expected to play an expanding role in tribology.In the following chapter we present an overview of the major results from the growing simulation literature. The emphasis is on providing a coherent picture of the field, rather than a historical review. We also outline opportunities for improved simulations, and highlight unanswered questions.We begin by presenting a brief overview of simulation techniques and focus on special features of simulations for tribological processes. For example, it is well known that the results of tribological experiments can be strongly influenced by the mechanical properties of the entire system that produces sliding. In much the same way, the results from simulations depend on how relative motion of the surfaces is imposed, and how heat generated by sliding is removed. The different techniques that are used are described, so that their influence on results can be understood in later sections.The complexities of realistic three-dimensional systems can make it difficult to analyze the molecular mechanisms that underly friction. The third section focuses on dry, wearless friction in less complex systems. The discussion begins with simple one-dimensional models of friction between crystalline surfaces. These models illustrate general results for the origin and trends of static and kinetic friction, such as the importance of metastability and the effect of commensurability. Then two-dimensional studies are described, with an emphasis ...

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Dynamics of friction: superlubric state

Cited by 36 publications

References 0 publications

Velocity tuning of friction with two trapped atoms

Velocity tuning of friction with two trapped atoms

Stability of Low-Friction Surface Sliding of Nanocrystals with Rectangular Symmetry and Application to W on NaF(001)

Computer Simulations of Friction, Lubrication, and Wear

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