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Efficient simulations with electronic open boundaries

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Title: Efficient simulations with electronic open boundaries
Authors: Horsfield, AP
Boleininger, M
D'Agosta, R
Iyer, V
Thong, A
Todorov, T
White, C
Item Type: Journal Article
Abstract: We present a reformulation of the Hairy Probe method for introducing electronic open boundaries that is appropriate for steady state calculations involving non-orthogonal atomic basis sets. As a check on the correctness of the method we investigate a perfect atomic wire of Cu atoms, and a perfect non-orthogonal chain of H atoms. For both atom chains we find that the conductance has a value of exactly one quantum unit, and that this is rather insensitive to the strength of coupling of the probes to the system, provided values of the coupling are of the same order as the mean inter-level spacing of the system without probes. For the Cu atom chain we find in addition that away from the regions with probes attached, the potential in the wire is uniform, while within them it follows a predicted exponential variation with position. We then apply the method to an initial investigation of the suitability of graphene as a contact material for molecular electronics. We perform calculations on a carbon nanoribbon to determine the correct coupling strength of the probes to the graphene, and obtain a conductance of about two quantum units corresponding to two bands crossing the Fermi surface. We then compute the current through a benzene molecule attached to two graphene contacts and find only a very weak current because of the disruption of the π-conjugation by the covalent bond between the benzene and the graphene. In all cases we find that very strong or weak probe couplings suppress the current.
Issue Date: 10-Aug-2016
Date of Acceptance: 29-Jul-2016
URI: http://hdl.handle.net/10044/1/38351
DOI: 10.1103/PhysRevB.94.075118
ISSN: 1550-235X
Publisher: American Physical Society
Journal / Book Title: Physical Review B
Volume: 94
Sponsor/Funder: European Office Of Aerospace Research & Developmen
The Leverhulme Trust
Funder's Grant Number: FA8655-12-1-2105
Keywords: Science & Technology
Physical Sciences
Physics, Condensed Matter
Fluids & Plasmas
02 Physical Sciences
03 Chemical Sciences
Publication Status: Published
Article Number: 075118
Appears in Collections:Materials
Faculty of Natural Sciences
Faculty of Engineering

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