Atomic scale friction of molecular adsorbates during diffusion

B. A.J. Lechner, A. S. De Wijn, H. Hedgeland, A. P. Jardine, B. J. Hinch, W. Allison, J. Ellis

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17 Scopus citations

Abstract

Experimental observations suggest that molecular adsorbates exhibit a larger friction coefficient than atomic species of comparable mass, yet the origin of this increased friction is not well understood. We present a study of the microscopic origins of friction experienced by molecular adsorbates during surface diffusion. Helium spin-echo measurements of a range of five-membered aromatic molecules, cyclopentadienyl, pyrrole, and thiophene, on a copper(111) surface are compared with molecular dynamics simulations of the respective systems. The adsorbates have different chemical interactions with the surface and differ in bonding geometry, yet the measurements show that the friction is greater than 2 ps-1 for all these molecules. We demonstrate that the internal and external degrees of freedom of these adsorbate species are a key factor in the underlying microscopic processes and identify the rotation modes as the ones contributing most to the total measured friction coefficient.

Original languageEnglish (US)
Article number194710
JournalJournal of Chemical Physics
Volume138
Issue number19
DOIs
StatePublished - May 21 2013

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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