Exploring the bonding of large hydrocarbons on noble metals: Diindoperylene on Cu(111), Ag(111), and Au(111)

Abstract

We present a benchmark study for the adsorption of a large π -conjugated organic molecule on different noble metal surfaces, which is based on x-ray standing wave (XSW) measurements and density functional theory calculations with van der Waals (vdW) interactions. The bonding distances of diindenoperylene on Cu(111), Ag(111), and Au (111) surfaces (2.51, 3.01, and 3.10Å, respectively) determined with the normal-incidence XSW technique are compared with calculations. Excellent agreement with the experimental data, i.e., deviations less than 0.1Å, is achieved using the Perdew-Burke-Ernzerhof (PBE) functional with vdW interactions that include the collective response of substrate electrons (the PBE + vdW surf method). It is noteworthy that the calculations show that the vdW contribution to the adsorption energy increases in the order Au(111) < Ag(111) < Cu(111).

Electronic charge rearrangement at metal/organic interfaces induced by weak van der Waals interactions

“…DIP has been studied extensively in monolayer on coinage metal surfaces [54][55][56]. The comparison between the equilibrium distance d C obtained with PBE + vdW surf and XSW experiments (Table I) shows an excellent agreement [11]. For what concerns E b , self-consistency leads to a tiny reduction (1.25%) of the PBE + vdW surf value.…”

“…In this context, the long-range van der Waals (vdW) interactions-while absent in standard DFT exchangecorrelation (XC) functionals-have been proven of fundamental importance in determining the structure and the cohesive energies of layered systems, such as molecules adsorbed on metal surfaces [3,[7][8][9][10][11][12][13][14]. On the other hand, the long-range vdW energy represents only a small fraction (0.001%) of the total electronic energy for a wide range of systems [15], from small dimers (e.g., diatomic dimers, water dimer) to complex hybrid inorganic/organic systems, passing through large molecular systems and metal surfaces.…”

First-Principles Models for van der Waals Interactions in Molecules and Materials: Concepts, Theory, and Applications

“…The vdW contribution to the binding energy of a diindenoperylene molecule (C 32 H 16 ) adsorbed on the Cu (111) surface is approximately 5.3 eV. 75 In this case, an error of 20% in the vdW coefficient would translate to an error of 1.0 eV in the equilibrium binding energyexceeding the energy of thermal fluctuations (kT) at room temperature by a factor of 35. We note that, in popular pairwise vdW corrections, vdW coefficients of molecules on metal surfaces can be overestimated by as much as 500%, because these approaches miss the complex polarization effects in the extended surface that are typically responsible for reducing the vdW coefficients of atoms in metals by 50−500% with respect to the free-atom values.…”

Self-Assembly of Bicomponent Molecular Monolayers: Adsorption Height Changes and Their Consequences

“…3,4 This technique has been applied to a number of molecules on various surfaces. [5][6][7][8][9][10][11][12][13] Here we report the use of XSW to determine the molecule-substrate distances in donor-acceptor molecular blends, which are not only highly relevant for many organic devices, but also have interfacial properties often differing from those of the corresponding single component layers. 14 In this work we provide a complete structural characterization of the first monolayer of a stoichiometric 1:1 donor-acceptor mixture assembled on Ag(111) and Cu(111) substrates.…”