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Ji, Wei; Zotti, Linda A.; Gao, HJ; Hofer, Werner A.

doi:10.1103/physrevlett.102.136809

Cited by 133 publications

(77 citation statements)

References 29 publications

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“…Furthermore, the LDOS calculations show three orbitals which are all predominantly located at the pyridine ring. From the electronic point of view, the presence of nitrogen in conjugated heterocyclic molecules lowers their -orbital energies while some of the orbitals are pushed to higher binding energies [17][18][19]. This feature can be seen for all adsorption geometries shown in Fig.…”

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Electronic Mapping of Molecular Orbitals at the Molecule-Metal Interface

et al. 2010

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The molecule-metal interface formed by pyridine-2,5-dicarboxylic acid chemically bonded to the Cu (110) surface is investigated by scanning tunneling microscopy and first-principles calculations. Our current-voltage spectroscopy studies reveal an electronic mapping of molecular orbitals as a function of tip position. By combining experimental and theoretical investigations, individual molecular orbitals are characterized by their energy and spatial distribution. The importance of adsorption geometries and conformational changes on the electron transport properties is highlighted. DOI: 10.1103/PhysRevLett.105.066801 PACS numbers: 73.63.Àb, 31.15.AÀ, 68.37.Ef, 82.37.Gk In the past decade, we have witnessed significant progress in integrating organic molecules in functional molecular devices like single molecule diodes [1,2] or in organic field-effect transistors [3,4]. To improve the functionality of such molecular electronic devices, an essential prerequisite is to gain a substantial understanding of the electronic structure of molecule-surface interfaces near the Fermi level that ultimately controls the performance of such a device [5][6][7].In this context, the precise energetic alignment of the molecular orbitals with respect to the Fermi level of the substrate, in particular, that of the highest occupied molecular orbitals and the lowest unoccupied molecular orbitals, is a key component of the electronic structure of the molecule-surface system under consideration. Therefore, in this Letter we present a detailed electronic mapping of molecular orbitals (MOs) by distance-dependent currentvoltage (I-V) spectroscopy. Combining the spatially resolved scanning tunneling spectroscopy (STS) results with density functional theory (DFT) investigations, we show how to identify the electronic structure of a molecule chemically bonded to a metallic surface. As a model system we investigate the adsorption of the pyridine-2,5-dicarboxylic acid (PyDCAH 2 ) on Cu(110).Our ab initio total-energy calculations have been performed in the framework of DFT [8] by using the PerdewBurke-Ernzerhof [9] exchange-correlation energy functional as implemented in the VASP code [10,11]. A detailed description is available in the supplementary material [12]. We first note that, in the case of the PyDCAH 2 molecule, which adsorbs on the Cu(110) surface under deprotonation of one carboxyl group, forming PyDCAH, several different adsorption geometries must be taken into account due to the presence of a nitrogen atom in the aromatic ring. Therefore, we differentiate in the following between C 7 H 4 N ð2Þ O 4 , describing a PyDCAH molecule with the nitrogen on position two in the ring (counting the ring atoms from the carbon atom located at the bonded carboxylate unit), and C 7 H 4 N ð3Þ O 4 , denoted as configuration f1g and f2g, respectively. Experimentally, there is no possibility to influence the orientation of the molecule during the adsorption process or to monitor topographically which configuration is preferentially adsorbed. If the ...

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Electronic Mapping of Molecular Orbitals at the Molecule-Metal Interface

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“…As is well known, GGA cannot describe the long-range van der Waals ͑vdW͒ forces, 11,12,39,[41][42][43] which dominate the interaction between organic molecules and metal surfaces. Thus, we employ the semiempirical vdW ͑DFT-D͒ method [44][45][46][47][48][49] and the vdW-DF method 50,51 to describe the vdW interactions.…”

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Density functional theoretical study of pentacene/noble metal interfaces with van der Waals corrections: Vacuum level shifts and electronic structures

Toyoda

Hamada

Lee

et al. 2010

The Journal of Chemical Physics

128

161

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In order to clarify factors determining the interface dipole, we have studied the electronic structures of pentacene adsorbed on Cu͑111͒, Ag͑111͒, and Au͑111͒ by using first-principles density functional theoretical calculations. In the structural optimization, a semiempirical van der Waals ͑vdW͒ approach ͓S. Grimme, J. Comput. Chem. 27, 1787 ͑2006͔͒ is employed to include long-range vdW interactions and is shown to reproduce pentacene-metal distances quite accurately. The pentacene-metal distances for Cu, Ag, and Au are evaluated to be 0.24, 0.29, and 0.32 nm, respectively, and work function changes calculated by using the theoretically optimized adsorption geometries are in good agreement with the experimental values, indicating the validity of the present approach in the prediction of the interface dipole at metal/organic interfaces. We examined systematically how the geometric factors, especially the pentacene-substrate distance ͑Z C ͒, and the electronic properties of the metal substrates contribute to the interface dipole. We found that at Z C Ն 0.35 nm, the work function changes ͑⌬'s͒ do not depend on the substrate work function ͑ m ͒, indicating that the interface level alignment is nearly in the Schottky limit, whereas at Z C Յ 0.25 nm, ⌬'s vary nearly linearly with m , and the interface level alignment is in the Bardeen limit. Our results indicate the importance of both the geometric and the electronic factors in predicting the interface dipoles. The calculated electronic structure shows that on Au, the long-range vdW interaction dominates the pentacene-substrate interaction, whereas on Cu and Ag, the chemical hybridization contributes to the interaction.

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“…vdW-DF has been used in a series of firstprinciple studies of sparse matter, 21 yielding, for example, new insight to the twist of DNA, 22 nanotube bundles, 23 water hexamers, 24 metal-organic frameworks, 25 and the binding mechanisms at organic metal interfaces. [26][27][28][29] In this paper, we first demonstrate that vdW-DF permits structural determination of molecular crystals and second assess the character of the attractive dispersion interactions. For the first, we calculate the lattice parameters for crystals of the cagelike hexamine, dodecahedrane, and cubane molecules.…”

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confidence: 99%

Structure and binding in crystals of cagelike molecules: Hexamine and platonic hydrocarbons

Berland

Hyldgaard

2010

The Journal of Chemical Physics

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In this paper, we show that first-principle calculations using a van der Waals density functional ͑vdW-DF͒ ͓M. Dion, H. Rydberg, E. Schröder, D. C. Langreth, and B. I. Lundqvist, Phys. Rev. Lett. 92, 246401 ͑2004͔͒ permit the determination of molecular crystal structure within density functional theory ͑DFT͒. We study the crystal structures of hexamine and the platonic hydrocarbons ͑cubane and dodecahedrane͒. The calculated lattice parameters and cohesion energy agree well with experiments. Further, we examine the asymptotic accounts of the van der Waals forces by comparing full vdW-DF with asymptotic atom-based pair potentials extracted from vdW-DF. The character of the binding differs in the two cases, with vdW-DF giving a significant enhancement at intermediate and relevant binding separations. We analyze consequences of this result for methods such as DFT-D and question DFT-D's transferability over the full range of separations.

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Chemical versus van der Waals Interaction: The Role of the Heteroatom in the Flat Absorption of Aromatic MoleculesC6H6,C5

Cited by 133 publications

References 29 publications

Electronic Mapping of Molecular Orbitals at the Molecule-Metal Interface

Electronic Mapping of Molecular Orbitals at the Molecule-Metal Interface

Density functional theoretical study of pentacene/noble metal interfaces with van der Waals corrections: Vacuum level shifts and electronic structures

Structure and binding in crystals of cagelike molecules: Hexamine and platonic hydrocarbons

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