Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 17: Nanotribulogy
O 17.4: Vortrag
Montag, 26. März 2012, 16:45–17:00, A 053
Direction dependence of friction for commensurate and moderately incommensurate surfaces — •Michael Wolloch1,2, Peter Mohn1, Josef Redinger1, and András Vernes1,2 — 1CMS, Institute of Applied Physics, Vienna University of Technology, Gußhausstraße 25-25a, 1040 Vienna, Austria — 2Austrian Center of Competence for Tribology, Viktor-Kaplan-Strasse 2, 2700 Wiener Neustadt, Austria
We present results from our calculations of quasi-static sliding of two atomically flat surfaces in dry, wearless contact using the Density Functional Theory package VASP. The main focus of our work was to determine to which extent commensurability of the surfaces and the sliding direction effects the friction force. The examined systems include commensurable fcc (111) Aluminium slabs and moderately incommensurate surfaces like bcc (110) Titanium on hcp (001) Titanium. A model consistent with stick-slip friction was devised to calculate the friction forces along sliding paths of up to 1 µm on a quantum mechanical basis. To map all forces and energies for rigid and relaxed atomic positions the top slab was scanned over the bottom one on a properly fine grid, which covers the entire unit cell. In this manner, it is shown that the mean friction force depends on the sliding direction and that due to relaxations incommensurate paths may result, counter-intuitively, in higher friction then commensurate ones.