Quantitative Prediction of Molecular Adsorption: Structure and Binding of Benzene on Coinage Metals

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Quantitative Prediction of Molecular Adsorption: Structure and Binding of Benzene on Coinage Metals

Wei Liu, Friedrich Maaß, Martin Willenbockel, Christopher Bronner, Michael Schulze, Serguei Soubatch, F. Stefan Tautz, Petra Tegeder, and Alexandre Tkatchenko

Phys. Rev. Lett. 115, 036104 – Published 17 July 2015

Abstract

Interfaces between organic molecules and solid surfaces play a prominent role in heterogeneous catalysis, molecular sensors and switches, light-emitting diodes, and photovoltaics. The properties and the ensuing function of such hybrid interfaces often depend exponentially on molecular adsorption heights and binding strengths, calling for well-established benchmarks of these two quantities. Here we present systematic measurements that enable us to quantify the interaction of benzene with the Ag(111) coinage metal substrate with unprecedented accuracy (0.02 Å in the vertical adsorption height and 0.05 eV in the binding strength) by means of normal-incidence x-ray standing waves and temperature-programed desorption techniques. Based on these accurate experimental benchmarks for a prototypical molecule-solid interface, we demonstrate that recently developed first-principles calculations that explicitly account for the nonlocality of electronic exchange and correlation effects are able to determine the structure and stability of benzene on the Ag(111) surface within experimental error bars. Remarkably, such precise experiments and calculations demonstrate that despite different electronic properties of copper, silver, and gold, the binding strength of benzene is equal on the (111) surface of these three coinage metals. Our results suggest the existence of universal binding energy trends for aromatic molecules on surfaces.

Received 24 April 2015

DOI:https://doi.org/10.1103/PhysRevLett.115.036104

This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Published by the American Physical Society

Authors & Affiliations

Wei Liu^1,5, Friedrich Maaß², Martin Willenbockel³, Christopher Bronner², Michael Schulze², Serguei Soubatch³, F. Stefan Tautz^3,4, Petra Tegeder², and Alexandre Tkatchenko^1,*

¹Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
²Physikalisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 253, 69120 Heidelberg, Germany
³Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
⁴Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
⁵Nano Structural Materials Center, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, Jiangsu, China

^*Corresponding author. tkatchenko@fhi-berlin.mpg.de

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Issue

Vol. 115, Iss. 3 — 17 July 2015

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Figure 1
The structure of Bz on Ag(111) as measured by NIXSW. (a) C1s x-ray photoelectron spectroscopy spectrum of $Bz / Ag (111)$ with a single component at 284.3 eV, recorded with $E^{h ν} = 2620 eV$ . The area of this carbon contribution is used to determine the electron yield in the NIXSW analysis. (b) Schematic of the NIXSW experiment. The x-ray standing wave field is shown as yellow color gradient, dark yellow meaning high x-ray intensity, and as an intensity curve $I (z)$ on the right. Photoemitters are shown in blue for two situations: a sharp distribution with coherent fraction $F_{c} = 1$ on the left, and a homogeneous distribution with $F_{c} \approx 0$ on the right. The coherent position ( $P_{c}$ ), indicated by the red arrow, runs from 0 to 1 between two consecutive Bragg planes of the substrate. As the photon energy is tuned through the Bragg condition, the nodes of the standing wave field shift by half a lattice constant, as indicated by the intensity $I (z)$ . (c) Blue dots: normalized electron yield of a NIXSW experiment for $Bz / Ag (111)$ . According to dynamical scattering theory, the normalized electron yield varies between 0 and 4. Yellow dots: corresponding reflectivity curve. Lines are the fits obtained with the Torricelli program [25, 26] from which $P_{c}$ and $F_{c}$ have been determined. (d) Polar diagram of the NIXSW result, with $P_{c}$ as polar angle and $F_{c}$ as radius. The high $F_{c}$ ( $≲ 1$ ) indicates a flat adsorption geometry of $Bz / Ag (111)$ [cf. left part of panel (b)].
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Figure 2
The desorption energy of benzene on Ag(111) as measured by TPD. (a) TPD spectra of benzene adsorbed on Ag(111) for different initial coverages recorded with a linear heating rate of $1 K / s$ at the mass of the parent ion 78 amu. (b) The logarithm of the desorption rate (in arbitrary units) as a function of the inverse temperature at an exemplary coverage of $θ = 0.1 ML$ . The slope ( $- E_{des} / k_{B}$ ) of the line yields the desorption energy ( $E_{des}$ ) for that coverage.
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Figure 3
First-principles calculations for benzene on Ag(111). Binding energy $E_{ads}$ as a function of vertical distance $d_{Ads}$ of benzene molecule center of mass from Ag(111). Calculations were carried out using three methods: semilocal Perdew-Burke-Ernzerhof (PBE) [42] functional with many-body dispersion (MBD) [37, 38] interactions, or hybrid Heyd-Scuseria-Ernzerhof (HSE) functional [35, 36] with either ${v d W}^{surf}$ [17] or MBD methods for including vdW interactions. Zero-point vibrational energy is included in all binding curves, calculated using a quasiharmonic approximation. The dotted lines indicate experimental equilibrium values of $d_{Ads}$ and $E_{Ads}$ with shaded regions corresponding to the associated error bars.
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