Friction–Load Relationship in the Adhesive Regime Revealing Potential Incapability of AFM Investigations
Reduced friction with increasing normal load in the adhesive regime is revealed by vdW-corrected DFT calculations of various rigid junction models such as Graphene/Graphene, h-BN/h-BN, and Graphene/h-BN. The origin of the friction–load relationship arises from the decreased sliding potential corrugation with increased normal load in the attractive regime of the interfacial separation above its equilibrium. The “negative” coefficient of friction behavior, which is mainly dominated by van der Waals attraction, is expected to appear in many interfaces without significant deformation. However, the friction behavior presented here may be inaccessible to atomic forces microscope (AFM) due to the intrinsic instability. The instruments such as interfacial forces microscope with force-feedback sensor or quartz tuning forks with large stiffness are proposed to measure friction behaviors in the entire attractive region.
This work was supported by the National Natural Science Foundation of China (Nos. 51775535 and 11972344), the Fundamental Research Funds for the Central Universities (No. 2682019CX29), Open Project of State Key Laboratory of Solid Lubrication (No. LSL-1910) and Guangdong Natural Science Foundation Project (No. 2018A030310001).
DFT-Grimme calculated separation z dependence of the binding energy, normal load, and friction force for sliding systems of Gr/Gr, h-BN/h-BN, and Gr/h-BN; DFT binding energy and friction forces for Gr/Gr; detailed DFT-TS binding energy, normal load, and friction force, and discussion about negative friction coefficient for h-BN/h-BN and Gr/h-BN sliding systems.
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Conflict of interest
The authors declare no competing financial interest.
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