One-Dimensional Strain Solitons Manipulated Superlubricity on Graphene Interface

Abstract

The frictional properties of a uniaxial tensile strained graphene interface are studied using molecular dynamics simulations. A misfit interval statistical method (MISM) is applied to characterize the atomistic misfits at the interface and strain soliton pattern. During sliding along both armchair and zigzag directions, the lateral force depends on the ratio of graphene flake length (L) to strain soliton spacing (L s ) and becomes nearly zero when L is an integer multiple of 3L s . Furthermore, the strain solitons propagate along the armchair sliding direction dynamically, while fission and fusion are repeatedly evidenced along the zigzag sliding direction. The underlying superlubric mechanism is revealed by a single-atom quasi-static model. The cancellation of lateral force for the contacting atoms exhibits a dynamic balance when sliding along the armchair direction but a quasi-static balance along the zigzag direction. A diagram of flake length with respect to tensile strain (L−ε) is proposed to predict the critical condition for the transition from nonsuperlubricity to superlubricity. Our results provide insights on the design of superlubric devices.

Deformation Coupled Moiré Mapping of Superlubricity in Graphene

“…The destruction of the moiré pattern induced by substrate surface roughness is considered a major obstacle in engineering superlubricity. In this part, we attempt to reproduce the moiré patterns of different models using a misfit interval statistic method. , Intriguingly, moiré patterns persist in various models, exhibiting moderate distortion despite the out-of-plane deformations shown in Figure c. Furthermore, the geometrical morphology of the distorted moiré pattern in different models displays little dependence on the number of lubricating layers, failing to account for the corresponding friction variation (Figure b).…”

“…To obtain a stable friction signal, the slider is twisted by 0.75° to form an incommensurate contact with the lubricating layers. As superlubricity exhibits little anisotropy with respect to sliding direction, and our previous studies ,, and research by other group demonstrated that a single representative direction is sufficient to capture the sliding behaviors in the modeling, we focus on sliding along the armchair direction, as shown in the top view of Figure b. The zigzag and armchair edges of the graphene lubricating layers are parallel to the x and y directions, respectively.…”

Structural Superlubricity of Two-Dimensional Materials: Mechanisms, Properties, Influencing Factors, and Applications

“…The elastic effect was a result of the principle that local lattice mismatch caused a change in the stacking of interlayer atoms, leading to the formation of local AB-stacked (commensurate) domains and AA-stacked domains. When the layers slid relative to each other, shear strain was generated along the boundary between the two domain walls, forming a localized strain soliton, which is also called saddle point (SP) stacking [81,99,100]. An elastic model for MD simulations was utilized to examine the impact of surface elasticity on the superlubricity phenomenon of multilayer graphite flakes in contact with a graphite substrate of 120 nm × 120 nm [81].…”

“…The shape of the moiré pattern under superlubricity shows a normal distribution (Figure 7(a 3 )). Based on this, how the persistence of moiré superlattice shape-induced superlubricity is affected by the twist angle and contact size was investigated, noteworthily, a critical twist angle of 1.5 • and a critical ratio of the contact size D to moiré period (the length of the strain soliton) [100]; L m , are required for robust superlubricity (Figure 7(a 1 ,a 2 )) [96]. The tribological behavior of a multilayer graphene moiré superlattice was further investigated by considering the effect of elastic deformation on the moiré superlattice shape-induced superlubricity [108].…”