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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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Article information


Submitted
12 Aug 2014
Accepted
12 Sep 2014
First published
17 Sep 2014

Nanoscale, 2014,6, 13163-13168
Article type
Paper
Author version available

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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