title: Can molecular projected density of states (PDOS) be systematically used in electronic conductance analysis?
abstract: Using benzenediamine and benzenedithiol molecular junctions as benchmarks, we investigate the widespread analysis of the quantum transport conductance in terms of the projected density of states (PDOS) onto molecular orbitals (MOs). We first consider two different methods for identifying the relevant MOs: (1) diagonalization of the Hamiltonian of the isolated molecule and (2) diagonalization of a submatrix of the junction Hamiltonian constructed by considering only basis elements localized on the molecule. We find that these two methods can lead to substantially different MOs and hence PDOS. Furthermore, within Method 1, the PDOS can differ depending on the isolated molecule chosen to represent the molecular junction (e.g., with or without dangling bonds); within Method 2, the PDOS depends on the chosen basis set. We show that these differences can be critical when the PDOS is used to provide a physical interpretation of the conductance (especially when its value is small, as it happens typically at zero bias). In this work, we propose a new approach in an attempt to reconcile the two traditional methods. Although some improvements were achieved, the main problems remain unsolved. Our results raise more general questions and doubts on a PDOS-based analysis of the conductance.
authors.affiliation: Institute of Condensed Matter and Nanosciences, Université catholique de Louvain, Chemin des Étoiles 8, bte L7.03.01, 1348 Louvain-la-Neuve, Belgium ; European Theoretical Spectroscopy Facility (ETSF) ; Present address: Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Tonatiuh
authors.initials: T
authors.lastname: Rangel
authors.affiliation: Institute of Condensed Matter and Nanosciences, Université catholique de Louvain, Chemin des Étoiles 8, bte L7.03.01, 1348 Louvain-la-Neuve, Belgium ; European Theoretical Spectroscopy Facility (ETSF).
authors.forename: Gian-Marco
authors.initials: GM
authors.lastname: Rignanese
authors.affiliation: European Theoretical Spectroscopy Facility (ETSF) ; CNRS, Institut Néel, F-38042 Grenoble, France ; University Grenoble Alpes, F-38000 Grenoble, France.
authors.forename: Valerio
authors.initials: V
authors.lastname: Olevano
keywords: DFT-Landauer; benzene-diamine; benzene-dithiol; molecular electronics; nanoelectronics; quantum transport