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Issue 21, 2014
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Does rotational melting make molecular crystal surfaces more slippery?

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Abstract

The surface of a crystal made of roughly spherical molecules exposes, above its bulk rotational phase transition at T = Tr, a carpet of freely rotating molecules, possibly functioning as “nanobearings” in sliding friction. We explored by extensive molecular dynamics simulations the frictional and adhesion changes experienced by a sliding C60 flake on the surface of the prototype system C60 fullerite. At fixed flake orientation both quantities exhibit only a modest frictional drop of order 20% across the transition. However, adhesion and friction drop by a factor of ∼2 as the flake breaks its perfect angular alignment with the C60 surface lattice suggesting an entropy-driven aligned-misaligned switch during pull-off at Tr. The results can be of relevance for sliding Kr islands, where very little frictional differences were observed at Tr, but also to the sliding of C60-coated tip, where a remarkable factor ∼2 drop has been reported.

Graphical abstract: Does rotational melting make molecular crystal surfaces more slippery?

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Publication details

The article was received on 12 Aug 2014, accepted on 12 Sep 2014 and first published on 17 Sep 2014


Article type: Paper
DOI: 10.1039/C4NR04641B
Author version available: Download Author version (PDF)
Citation: Nanoscale, 2014,6, 13163-13168
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    Does rotational melting make molecular crystal surfaces more slippery?

    A. Benassi, A. Vanossi, C. A. Pignedoli, D. Passerone and E. Tosatti, Nanoscale, 2014, 6, 13163
    DOI: 10.1039/C4NR04641B

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