Co(CO)n/Cu(001): Towards understanding chemical control of the Kondo effect

Bahlke, Marc Philipp; Wahl, Peter; Diekhöner, Lars; Herrmann, Carmen

doi:10.1063/1.5079518

Cited by 6 publications

(15 citation statements)

References 71 publications

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“…27,28 In particular the accurate first-principles description of molecule-metal interfaces in general is not trivial due to the formation of dipole layers in this region, which is particularly important in case of SAMs. [62][63][64][67][68][69][70][71][72][73][74]…”

Section: Opti N Wiresmentioning

confidence: 99%

Toward a First-Principles Evaluation of Transport Mechanisms in Molecular Wires

Kröncke

Herrmann

2020

J. Chem. Theory Comput.

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Understanding charge transport through molecular wires is important for nanoscale electronics and biochemistry. Our goal is to establish a simple first-principles protocol for predicting the charge transport mechanism in such wires, in particular the crossover from coherent tunneling for short wires to incoherent hopping for longer wires. This protocol is based on a combination of density-functional theory with a polarizable continuum model introduced by Kaupp et al. for mixed-valence molecules, which we had previously found to work well for length-dependent charge delocalization in such systems. We combine this protocol with a new charge delocalization measure tailored for molecular wires, and we show that it can predict the tunneling-to hopping transition length with a maximum error of one subunit in five sets of molecular wires studied experimentally in molecular junctions at room temperature. This suggests that the protocol is also well suited for estimating the extent of hopping sites as relevant, e.g., for the intermediate tunneling-hopping regime in DNA. File list (3) download file view on ChemRxiv ms.pdf (1.59 MiB) download file view on ChemRxiv supporting_information.pdf (3.90 MiB) download file view on ChemRxiv cartesian_coordinates.zip (33.23 KiB)

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Section: Opti N Wiresmentioning

confidence: 99%

Toward a First-Principles Evaluation of Transport Mechanisms in Molecular Wires

Kröncke

Herrmann

2020

J. Chem. Theory Comput.

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“…However, a first estimate based on cutting away parts of the system suggested that this enhancement is indirectly (see Figure 4) caused by CO-surface interactions, i.e., by the ligands affecting how the surface interacts with the Co atom [35]. This was supported by an analysis of the density of states.…”

Section: Co(co) 4 /Cu(001)mentioning

confidence: 94%

“…For the Kondo-relevant orbital 3d x 2 −y 2 in Co(CO) 4 /Cu(001), Im∆ ii (ω) was found to be increased in the range of ω = −3.0 to 2.0 eV, with a significant enhancement of the hybridization at ω = −2.0 eV, as compared to an isolated Co atom on Cu(001) [35]. Naively, one would expect the hybridization of the Co 3d orbitals in the carbonyl species to be smaller than for an isolated Co on Cu(001), because of the increased Co-surface distance of 1.85Å in Co(CO) 4 /Cu(001) compared with 1.78Å in Co/Cu(001).…”

Section: Co(co) 4 /Cu(001)mentioning

confidence: 96%

“…This was done in Ref. [35]. However, such a procedure does not take into account that different parts of the environment do not only influence the correlated subsystem, but also each other electronically.…”

Section: Modelmentioning

confidence: 99%

“…For example, if the unpaired spin is located on a transition metal atom surrounded by one or several ligands, to what extent is the hybridization function determined by interactions of the unpaired spin with the ligands, and to what extent by interactions with the surface? So far, such questions have been adressed by removing different parts of the system (e.g the ligands) and by comparing the resulting hybridization function with the full one [34,35]. This has the drawback that removing parts of the system may affect its electronic structure in undesired ways.…”

Section: Introductionmentioning

confidence: 99%

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Local Decomposition of Hybridization Functions: Chemical Insight into Correlated Molecular Adsorbates

Bahlke¹,

Schneeberger²,

Herrmann

2021

Preprint

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Hybridization functions are an established tool for investigating the coupling between a correlated subsystem (often a single transition metal atom) and its uncorrelated environment (the substrate and any ligands present). The hybridization function can provide valuable insight into why and how strong correlation features such as the Kondo effect can be chemically controlled in certain molecular adsorbates. To deepen this insight, we introduce a local decomposition of the hybridization function, based on a truncated cluster approach, enabling us to study individual effects on this function coming from specific parts of the systems (e.g., the surface, ligands, or parts of larger ligands). It is shown that a truncated-cluster approach can reproduce the Co 3d and Mn 3d hybridization functions from periodic boundary conditions in Co(CO)4/Cu(001) and MnPc/Ag(001) qualitatively well. By locally decomposing the hybridization functions, it is demonstrated at which energies the transition metal atoms are mainly hybridized with the substrate or with the ligand. For the Kondo-active the 3dx2−y2 orbital in Co(CO)4/Cu(001), the hybridization function at the Fermi energy is substrate-dominated, so we can assign its enhancement compared with ligand-free Co to an indirect effect of ligand–substrate interactions. In MnPc/Ag(001), the same is true for the Kondo-active orbital, but for two other orbitals, there are both direct and indirect effects of the ligand, together resulting in such strong screening that their potential Kondo activity is suppressed. A local decomposition of hybridization functions could also be useful in other areas, such as analyzing the electrode self-energies in molecular junctions.

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Design Considerations for Oligo(p-phenyleneethynylene) Organic Radicals in Molecular Junctions

et al. 2021

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Spin polarization in the electron transmission of radicals is important for understanding single-molecule conductance experiments focusing on shot noise, Kondo properties, or magnetoresistance. We study how stable radical substituents can affect such spin polarization when attached to oligo(p-phenyleneethynylene) (OPE) backbones. We find that it is not straightforward to translate the spin density on a stable radical substituent into spin-dependent transmission for the para-connected wires under study here, owing to increased steric interactions compared with meta-connected wires, and a resulting twisting of the radical substituent and OPE π systems. The most promising example is a t-butyl nitroxide substituent, which, despite little pronounced spin delocalization onto the backbone, yields a spindependent transmission feature, which one might be able to shift toward the Fermi energy by additional substituents. We also find that for bulkier substituents, dispersion interactions with the substituent can lead to twisting of one of the outer OPE rings, reducing the overall conductance. As a further potential design consideration, attaching radicals via linkers might increase the possibilities for spin-dependent intermolecular and molecule− electrode interactions.

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Co(CO)n/Cu(001): Towards understanding chemical control of the Kondo effect

Cited by 6 publications

References 71 publications

Toward a First-Principles Evaluation of Transport Mechanisms in Molecular Wires

Toward a First-Principles Evaluation of Transport Mechanisms in Molecular Wires

Local Decomposition of Hybridization Functions: Chemical Insight into Correlated Molecular Adsorbates

Design Considerations for Oligo(p-phenyleneethynylene) Organic Radicals in Molecular Junctions

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