title: Graphical prediction of quantum interference-induced transmission nodes in functionalized organic molecules.
abstract: Quantum interference (QI) in molecular transport junctions can lead to dramatic reductions of the electron transmission at certain energies. In a recent work [Markussen et al., Nano Lett., 2010, 10, 4260] we showed how the presence of such transmission nodes near the Fermi energy can be predicted solely from the structure of a conjugated molecule when the energies of the atomic p(z) orbitals do not vary too much. Here we relax the assumption of equal on-site energies and generalize the graphical scheme to molecules containing different atomic species. We use this diagrammatic scheme together with tight-binding and density functional theory calculations to investigate QI in linear molecular chains and aromatic molecules with different side groups. For the molecular chains we find a linear relation between the position of the transmission nodes and the side group π orbital energy. In contrast, the transmission functions of functionalized aromatic molecules generally display a rather complex nodal structure due to the interplay between molecular topology and the energy of the side group orbital.
authors.affiliation: Center for Atomic-scale Materials Design (CAMD), Department of Physics, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
authors.forename: Troels
authors.initials: T
authors.lastname: Markussen
authors.forename: Robert
authors.initials: R
authors.lastname: Stadler
authors.forename: Kristian S
authors.initials: KS
authors.lastname: Thygesen
mesh_terms: D009930:Organic Chemicals / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D009930:Organic Chemicals