Weak Intermolecular Interactions in an Ionically Bound Molecular Adsorbate:<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mtext mathvariant="normal">Cyclopentadienyl</mml:mtext><mml:mo>/</mml:mo><mml:mi>Cu</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mn>111</mml:mn><mml:mo stretchy="false">)</mml:mo></mml:math>

Hedgeland, Holly; Lechner, Barbara A. J.; Tuddenham, F. E.; Jardine, A. P.; Allison, W.; Ellis, John; Sacchi, Marco; Jenkins, Stephen J.; Hinch, B. J.

doi:10.1103/physrevlett.106.186101

Cited by 22 publications

(42 citation statements)

References 26 publications

(39 reference statements)

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“…In the past, HeSE experiments were analyzed by investigating each ISF individually [22,26]. Using that methodology, we found the lineshapes along 110 at 300 K exhibited little evidence for double decays, and estimated that fcc and hcp hollow sites are approximately degenerate [29]. Here we show how a Bayesian analysis can be employed to obtain a more accurate determination of E, confirming that the energy difference is indeed small, yet nonzero.…”

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confidence: 52%

“…Here, we demonstrate its power for 0.03 ML cyclopentadienyl (Cp), C 5 H 5 , on Cu(111), a model system which has been characterized in detail in a previous HeSE study [29]. We extend our earlier room-temperature study to 135 K where we are more sensitive to detecting small energy differences between adsorption sites.…”

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confidence: 62%

“…In our prior investigation of the Cp/Cu(111) dynamics we found that the molecule adsorbs preferentially on fcc and hcp hollow sites, hopping over an effective activation barrier of (41 ± 1) meV [29]. On the Cu(111) lattice, the two different types of hollow sites form a non-Bravais lattice with different jump directions for species originating at fcc and hcp sites, respectively, as illustrated in Fig.…”

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confidence: 89%

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Ultra-high precision determination of site energy differences using a Bayesian method

et al. 2014

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How to cite:Lechner, B. A. J.; Kole, P. R.; Hedgeland, H.; Jardine, A. P.; Allison, W.; Hinch, B. J. and Ellis, J. (2014). Ultra-high precision determination of site energy differences using a Bayesian method. Physical Review B, 89(12) For guidance on citations see FAQs. Accurate experimental data of adsorbate potential energy landscapes are crucial as benchmarks for the evaluation of first-principles calculations. Here, we present a Bayesian method, analyzing the difference in forward and backward hopping rate in helium spin-echo measurements, that allows us to determine the binding-energy difference between two sites with unprecedented accuracy. Demonstrating the power of the method on the model system cyclopentadienyl/Cu(111), we find an energy difference between fcc and hcp hollow sites of (10.6 ± 1.7) meV.

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confidence: 62%

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confidence: 89%

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Ultra-high precision determination of site energy differences using a Bayesian method

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“…We carried out we find that the dispersion-corrected DFT tends to overestimate the corrugation of the benzene/Cu(001) PES, but correctly predicts that the activation barriers for this system to be higher than for the similar systems of cyclopentadienyl/Cu(111) 28 and thiophene/Cu(111).…”

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confidence: 80%

“…25 The method was initially developed for alkali metal diffusion and has also been used with considerable success in the interpretation of data from benzene/graphite 26 and other small molecular systems. 2,[27][28][29] In the first instance, we treat the molecule as a point mass. Later we show that it is necessary to refine the treatment and consider the adsorbate as an extended molecular system.…”

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confidence: 99%

Mass Transport in Surface Diffusion of van der Waals Bonded Systems: Boosted by Rotations?

Hedgeland

Sacchi

Singh

et al. 2016

J. Phys. Chem. Lett.

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Mass transport at a surface is a key factor in heterogeneous catalysis. The rate is determined by excitation across a translational barrier and depends on the energy landscape and the coupling to the thermal bath of the surface. Here we use helium spin− echo spectroscopy to track the microscopic motion of benzene adsorbed on Cu(001) at low coverage (θ ∼ 0.07 ML). Specifically, our combined experimental and computational data determine both the absolute rate and mechanism of the molecular motion. The observed rate is significantly higher by a factor of 3.0 ± 0.1 than is possible in a conventional, point-particle model and can be understood only by including additional molecular (rotational) coordinates. We argue that the effect can be described as an entropic contribution that enhances the population of molecules in the transition state. The process is generally relevant to molecular systems and illustrates the importance of the pre-exponential factor alongside the activation barrier in studies of surface kinetics.

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Quantum Influences in the Diffusive Motion of Pyrrole on Cu(111)

et al. 2013

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The adsorption of aromatic molecules on surfaces is of broad interest in the fields of self-assembled networks and selforganized growth. [1,2] During self-assembly, adsorbates diffuse and adjust their orientation to form regular superstructures. The result is a delicate balance between supramolecular chemistry (dipole-dipole interactions, hydrogen bonding, and van der Waals forces) and molecule-surface interactions. These factors determine the structure, energy, site-specificity, and two-dimensional molecular translational and rotational diffusion. [2][3][4][5] Differently substituted polyaromatic rings form key building blocks, [6] defining the structure of chemically functionalized surfaces. It is crucial to understand the motion of single molecular precursors to gain insight into the complex processes underlying self-assembly. Aromatic adsorbates are extended particles of large mass that are assumed to obey classical mechanics for temperatures where self-assembly occurs. We will see, however, that quantum effects can nevertheless play a crucial role in the dynamics of surface diffusion even when the quantized degrees of freedom are not associated directly with translational motion.Here, we study pyrrole, C 4 H 4 NH, an important precursor for many chemically and technologically relevant materials. In recent years, functionalized pyrroles and related molecules have attracted increasing attention as self-assembling adsorbates. [7] Pyrrole has been studied on several metal surfaces, including Pt(111), [8] Pd (111), [9] Rh(111), [10] and Cu(100). [11] Whilst little is known about potential energy landscapes and interactions between molecules, pyrrole is usually found to adsorb in a flat-lying geometry at low coverages, often moving to a tilted geometry at higher coverages.Herein we describe a helium spin-echo (HeSE) and density functional theory (DFT) study of the dynamics of this elementary building block on Cu(111) to investigate interadsorbate interactions, the effect of friction, and the role of quantum modes in a sub-monolayer regime. We will show that the behavior is dominated by the quantum contribution to the total energy of pyrroles vibrational ground state. Surprisingly, the important vibrations are not those associated with motion of the center of mass but are internal modes.The HeSE method is new and uniquely sensitive to atomic scale motion on pico-to nanosecond timescales. [12] Figure 1 illustrates the principle, showing how surface motion occurring over a time difference, t SE , reduces coherent scattering and gives a correlation function that typically decays with time as f(t) = a exp(Àat SE ) + c. [12] The characteristic timescale of the motion is then given by the decay rate, a, which depends on the angle of scattering. Motion, in real space, is deduced by comparing the dependence on scattering angle, expressed as a momentum transfer, DK, with Langevin molecular dynamics (MD) simulations. [13] We have performed experiments at (121-170) K along two crystal directions. The resulting a(DK) depend...

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Weak Intermolecular Interactions in an Ionically Bound Molecular Adsorbate:Cyclopentadienyl/Cu(111)

Cited by 22 publications

References 26 publications

Ultra-high precision determination of site energy differences using a Bayesian method

Ultra-high precision determination of site energy differences using a Bayesian method

Mass Transport in Surface Diffusion of van der Waals Bonded Systems: Boosted by Rotations?

Quantum Influences in the Diffusive Motion of Pyrrole on Cu(111)

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