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Molecular Physics seminar

Anisotropy of nanoscale friction

by Astrid S. de Wijn (Molecuar Physics Division)

FB55 ()


Mechanical properties of crystalline materials are ultimately determined by their atomic structure. A direct consequence of the symmetry of the atomic surface structure is anisotropy of friction and wear. We investigate the anisotropy of friction theoretically, as well as experimentally on graphitic surfaces. We find that the anisotropy does not depend on the geometry of the sliding object, only on that of the substrate. Friction vectors can deviate significantly from the pulling directions. For graphitic substrates, the strongest deviations are found for pulling directions which lie almost along one zigzag direction of the honeycomb structure, the preferred sliding directions. Numerical simulation and further theory reveal the role of temperature and of the two-dimensional character of the surface potential for the friction anisotropy. The friction is determined by atomic stick-slip events along and across molecular rows determine direction and magnitude of friction. (Collaboration with Balakrishna S. G. and R. Bennewitz, INM - Leibniz Institute for New Materials, Germany) [1] Preferential sliding directions on graphite, Balakrishna S.G., Astrid S. de Wijn, and Roland Bennewitz, Phys. Rev. B 89, 245440 (2014).