Journal
CHEMPHYSCHEM
Volume 18, Issue 15, Pages 2033-2039Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/cphc.201700378
Keywords
adhesion; Amontons' law; density functional calculations; nanofriction; noncovalent interactions
Funding
- Young Thousand Talents Program of China
- National Natural Science Foundation of China [21602149, 21673095, 51631004]
- Program for New Century Excellent Talents in University [NCET-13-0255]
- computing resources of High Performance Computing Center of Jilin University and National Supercomputing Center in Jinan, China
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By means of a many-body van der Waals (vdW)-corrected density functional theory approach, the atomic-scale friction of a prototypical tip-substrate system consisting of an Si tip and a graphene substrate is studied. In a loading-sliding process, the tip-substrate distance is found to be essential for nanofrictional behavior, through determining the competition between vdW contributions and electronic contributions. As the tip approaches the substrate, this competition results in a smooth transition of normal forces from attraction to repulsion, and the friction coefficient in turn undergoes a sign change from negative to positive with possible giant magnitude and strong anisotropy. The loading-sliding process does not introduce any chemical modification of the underlying system. These findings reveal the boundary of validity of Amontons' law, unify negative and giant friction coefficients, rationalize the experimentally observed anisotropy of nanofriction, and are universal when vdW interactions are crucial, all of which are helpful to establish a comprehensive picture of nanofriction.
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