Atomic scale friction of molecular adsorbates during diffusion

Lechner, Barbara A. J.; Wijn, Astrid S. de; Hedgeland, Holly; Jardine, A. P.; Hinch, B. J.; Allison, W.; Ellis, John

doi:10.1063/1.4804269

Cited by 22 publications

(22 citation statements)

References 47 publications

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“…2(b), and in particular the significant fraction of double jumps, suggest that the observed motion lies in the low-friction regime. Notably, the finding differs from the observation of other molecular adsorbates which generally showed a higher friction 65 .…”

Section: Resultscontrasting

confidence: 99%

“…Based on the low corrugation of the PES (from experiment and DFT calculations) in combination with the rather small diffusion constant we may already anticipate that the system exhibits an unusual atomicscale friction. Friction in surface diffusion processes can be caused by a variety of dissipative mechanisms, interactions with phonons and electrons in the substrate 54 as well as interactions between adsorbates 64 and coupling of the internal molecular degrees of freedom with the motion of the centre of mass 65 . For Brownian motion, the atomic-scale friction η can be directly extracted with Einstein's relation 61,66 , while it is not possible for hopping motion.…”

Section: Resultsmentioning

confidence: 99%

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Nanoscopic diffusion of water on a topological insulator

et al. 2020

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The microscopic motion of water is a central question, but gaining experimental information about the interfacial dynamics of water in fields such as catalysis, biophysics and nanotribology is challenging due to its ultrafast motion, and the complex interplay of intermolecular and molecule-surface interactions. Here we present an experimental and computational study of the nanoscale-nanosecond motion of water at the surface of a topological insulator (TI), Bi 2 Te 3. Understanding the chemistry and motion of molecules on TI surfaces, while considered a key to design and manufacturing for future applications, has hitherto been hardly addressed experimentally. By combining helium spin-echo spectroscopy and density functional theory calculations, we are able to obtain a general insight into the diffusion of water on Bi 2 Te 3. Instead of Brownian motion, we find an activated jump diffusion mechanism. Signatures of correlated motion suggest unusual repulsive interactions between the water molecules. From the lineshape broadening we determine the diffusion coefficient, the diffusion energy and the pre-exponential factor.

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Section: Resultscontrasting

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Nanoscopic diffusion of water on a topological insulator

et al. 2020

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“…16 The data was simulated with Langevin dynamics in a two-dimensional adsorbate-substrate potential and included pairwise inter-adsorbate interactions. 19 To illustrate that further information can be obtained from the technique, we show, in Fig. In the analysis, we used data in the long-time limit to deduce the diffusive behaviour.…”

Section: Results and Analysismentioning

confidence: 99%

Vibrational lifetimes and friction in adsorbate motion determined from quasi-elastic scattering

Lechner

Hedgeland

Jardine

et al. 2015

Phys. Chem. Chem. Phys.

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The vibrational excitation of molecules adsorbed on a surface is typically probed by spectroscopic techniques such as infrared or Raman spectroscopy. In the present article we demonstrate an alternative method to determine vibrational lifetimes of adsorbate molecules using quasi-elastic helium atom scattering (QHAS). As a probe of diffusive motion of molecules on surfaces QHAS is well established. Here, we demonstrate that QHAS can also be used to probe the vibrational lifetime of a molecule in its adsorption well. Measurements of cyclopentadienyl, C5H5, on Cu(111) allow us to distinguish two substrate phonon modes as well as two molecular vibrational modes, perpendicular and parallel to the surface. We further find that the dephasing of the vibrational motion corresponds to the friction determined in previous diffusion measurements.

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“…Let {G} be three linearly independent first-order reciprocal lattice vectors of the surface, whose close packing distance in real space is a. Then, a simple Fourier series representation with the correct symmetry for the fcc(111) surface is given by 17,44…”

Section: B Two Spatial Dimensionsmentioning

confidence: 99%

Amplitude of jump motion signatures in classical vibration-jump dynamics

Townsend

Ellis

2018

The Journal of Chemical Physics

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The classical Langevin dynamics of a particle in a periodic potential energy landscape are studied via the intermediate scattering function (ISF). By construction, the particle performs coupled vibrational and activated jump motion with a wide separation of the vibrational period and the mean residence time between jumps.The long time limit of the ISF is a decaying tail proportional to the function that describes ideal jump motion in the absence of vibrations. The amplitude of the tail is unity in idealized jump dynamics models, but is reduced from unity by the intrawell motion. Analytical estimates of the amplitude of the jump motion signature are provided by assuming a factorization of the conditional probability density of the particle position at long times, motivated by the separation of time scales associated with inter-cell and intra-cell motion. The assumption leads to a factorization of the ISF at long correlation times, where one factor is an ideal jump motion signature, and the other component is the amplitude of the signature. The amplitude takes the form of a single-particle anharmonic Debye-Waller factor. The factorization approximation is exact at the diffraction conditions associated with the periodic potential. Numerical simulations of the Langevin equation in one and two spatial dimensions confirm that for a strongly corrugated potential the analytical approximation provides a good qualitative description of the trend in the jump signature amplitude, between the points where the factorization is exact. Published full-text https://doi.

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Atomic scale friction of molecular adsorbates during diffusion

Cited by 22 publications

References 47 publications

Nanoscopic diffusion of water on a topological insulator

Nanoscopic diffusion of water on a topological insulator

Vibrational lifetimes and friction in adsorbate motion determined from quasi-elastic scattering

Amplitude of jump motion signatures in classical vibration-jump dynamics

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