Stretching of BDT-gold molecular junctions: Thiol or thiolate termination?

Handle URI:
http://hdl.handle.net/10754/563260
Title:
Stretching of BDT-gold molecular junctions: Thiol or thiolate termination?
Authors:
Souza, Amaury De Melo; Rungger, Ivan; Pontes, Renato Borges; Rocha, Alexandre Reily; Da Silva, Antônio José Roque; Schwingenschlögl, Udo ( 0000-0003-4179-7231 ) ; Sanvito, S.
Abstract:
It is often assumed that the hydrogen atoms in the thiol groups of a benzene-1,4-dithiol dissociate when Au-benzene-1,4-dithiol-Au junctions are formed. We demonstrate, by stability and transport property calculations, that this assumption cannot be made. We show that the dissociative adsorption of methanethiol and benzene-1,4-dithiol molecules on a flat Au(111) surface is energetically unfavorable and that the activation barrier for this reaction is as high as 1 eV. For the molecule in the junction, our results show, for all electrode geometries studied, that the thiol junctions are energetically more stable than their thiolate counterparts. Due to the fact that density functional theory (DFT) within the local density approximation (LDA) underestimates the energy difference between the lowest unoccupied molecular orbital and the highest occupied molecular orbital by several electron-volts, and that it does not capture the renormalization of the energy levels due to the image charge effect, the conductance of the Au-benzene-1,4-dithiol-Au junctions is overestimated. After taking into account corrections due to image charge effects by means of constrained-DFT calculations and electrostatic classical models, we apply a scissor operator to correct the DFT energy level positions, and calculate the transport properties of the thiol and thiolate molecular junctions as a function of the electrode separation. For the thiol junctions, we show that the conductance decreases as the electrode separation increases, whereas the opposite trend is found for the thiolate junctions. Both behaviors have been observed in experiments, therefore pointing to the possible coexistence of both thiol and thiolate junctions. Moreover, the corrected conductance values, for both thiol and thiolate, are up to two orders of magnitude smaller than those calculated with DFT-LDA. This brings the theoretical results in quantitatively good agreement with experimental data.
KAUST Department:
Physical Sciences and Engineering (PSE) Division; Materials Science and Engineering Program; Computational Physics and Materials Science (CPMS)
Publisher:
Royal Society of Chemistry (RSC)
Journal:
Nanoscale
Issue Date:
2014
DOI:
10.1039/c4nr04081c
Type:
Article
ISSN:
20403364
Sponsors:
Research reported in this publication was supported by the King Abdullah University of Science and Technology (KAUST). The Trinity College High-Performance Computer Center and the HPC cluster at Universidade de Sao Paulo provided the computational resources.
Appears in Collections:
Articles; Physical Sciences and Engineering (PSE) Division; Materials Science and Engineering Program; Computational Physics and Materials Science (CPMS)

Full metadata record

DC FieldValue Language
dc.contributor.authorSouza, Amaury De Meloen
dc.contributor.authorRungger, Ivanen
dc.contributor.authorPontes, Renato Borgesen
dc.contributor.authorRocha, Alexandre Reilyen
dc.contributor.authorDa Silva, Antônio José Roqueen
dc.contributor.authorSchwingenschlögl, Udoen
dc.contributor.authorSanvito, S.en
dc.date.accessioned2015-08-03T11:44:20Zen
dc.date.available2015-08-03T11:44:20Zen
dc.date.issued2014en
dc.identifier.issn20403364en
dc.identifier.doi10.1039/c4nr04081cen
dc.identifier.urihttp://hdl.handle.net/10754/563260en
dc.description.abstractIt is often assumed that the hydrogen atoms in the thiol groups of a benzene-1,4-dithiol dissociate when Au-benzene-1,4-dithiol-Au junctions are formed. We demonstrate, by stability and transport property calculations, that this assumption cannot be made. We show that the dissociative adsorption of methanethiol and benzene-1,4-dithiol molecules on a flat Au(111) surface is energetically unfavorable and that the activation barrier for this reaction is as high as 1 eV. For the molecule in the junction, our results show, for all electrode geometries studied, that the thiol junctions are energetically more stable than their thiolate counterparts. Due to the fact that density functional theory (DFT) within the local density approximation (LDA) underestimates the energy difference between the lowest unoccupied molecular orbital and the highest occupied molecular orbital by several electron-volts, and that it does not capture the renormalization of the energy levels due to the image charge effect, the conductance of the Au-benzene-1,4-dithiol-Au junctions is overestimated. After taking into account corrections due to image charge effects by means of constrained-DFT calculations and electrostatic classical models, we apply a scissor operator to correct the DFT energy level positions, and calculate the transport properties of the thiol and thiolate molecular junctions as a function of the electrode separation. For the thiol junctions, we show that the conductance decreases as the electrode separation increases, whereas the opposite trend is found for the thiolate junctions. Both behaviors have been observed in experiments, therefore pointing to the possible coexistence of both thiol and thiolate junctions. Moreover, the corrected conductance values, for both thiol and thiolate, are up to two orders of magnitude smaller than those calculated with DFT-LDA. This brings the theoretical results in quantitatively good agreement with experimental data.en
dc.description.sponsorshipResearch reported in this publication was supported by the King Abdullah University of Science and Technology (KAUST). The Trinity College High-Performance Computer Center and the HPC cluster at Universidade de Sao Paulo provided the computational resources.en
dc.publisherRoyal Society of Chemistry (RSC)en
dc.titleStretching of BDT-gold molecular junctions: Thiol or thiolate termination?en
dc.typeArticleen
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
dc.contributor.departmentMaterials Science and Engineering Programen
dc.contributor.departmentComputational Physics and Materials Science (CPMS)en
dc.identifier.journalNanoscaleen
dc.contributor.institutionSchool of Physics, Trinity College Dublin, College Green D2, Irelanden
dc.contributor.institutionInstituto de Física, Universidade Federal de Goiás, Campus SamambaiaGoiânia-GO, Brazilen
dc.contributor.institutionInstituto de Física Teórica, Universidade Estadual Paulista, Barra-FundaSão Paulo, SP, Brazilen
dc.contributor.institutionInstituto de Física, Universidade de São Paulo, Cidade Universitária, Rua do MatãoSão Paulo, SP, Brazilen
dc.contributor.institutionLaboratório Nacional de Luz Sincroton LNLSCampinas, SP, Brazilen
kaust.authorSchwingenschlögl, Udoen
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