Electric conductance of a mechanically strained molecular junction from first principles: Crucial role of structural relaxation and conformation sampling

Nguyën, Huu Chuong; Szyja, Bartłomiej M.; Doltsinis, Nikos L.

doi:10.1103/physrevb.90.115440

Cited by 10 publications

(8 citation statements)

References 51 publications

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“…The pronounced inter est in these particular hybrid molecule-metal junctions and interfaces is due to a multitude of potential applications such as tailoring the properties of surfaces [3][4][5][6][7], chemical anchors for molecular electronics applications [8][9][10], or coating agents for the stabilization of gold nanoparticles [11,12]. Only lately, it has been realized that the consid eration of the mechanical properties of these moleculemetal hybrids becomes a crucial design factor [13][14][15][16][17][18][19][20][21][22][23][24] for nanoscale devices.…”

Section: Nanomechanics Of Bidentate Thiolate Ligands On Gold Surfacesmentioning

confidence: 99%

Nanomechanics of Bidentate Thiolate Ligands on Gold Surfaces

2015

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The effect of the chain length separating sulfur atoms in bidentate thiols attached to defective gold surfaces on the rupture of the respective molecule-gold junctions has been studied computationally. Thermal desorption always yields cyclic disulfides. In contrast, mechanochemical desorption leads to cyclic gold complexes, where metal atoms are extracted from the surface and kept in tweezer-like arrangements by the sulfur atoms. This phenomenon is rationalized in terms of directional mechanical manipulation of Au-Au bonds and Au-S coordination numbers. Moreover, the flexibility of the chain is shown to crucially impact on the mechanical strength of the junction.

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Section: Nanomechanics Of Bidentate Thiolate Ligands On Gold Surfacesmentioning

confidence: 99%

Nanomechanics of Bidentate Thiolate Ligands on Gold Surfaces

2015

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“…We now consider a more complex case: the benzene-dithiol (BDT)–gold junction. Experimental and theoretical works concluded that the BDT–gold junction can be stable in several different atomic structures/geometries [ 16 , 47 – 51 ]. To account for different hybridizations and bonding motifs, three geometries are studied here: the sulfur atom of the benzene-dithiol molecule can adsorb onto an extra gold adatom without losing the bound hydrogen atom (BDT-n); the benzene-dithiol molecule can lose the hydrogen atom, thus becoming benzene-dithiolate, and bind its sulfur atom to an extra gold adatom in a pyramidal structure (BDT-p); or the benzene-dithiolate can bind to three equidistant gold atoms in the hollow structure (BDT-h).…”

Section: Resultsmentioning

confidence: 99%

Can molecular projected density of states (PDOS) be systematically used in electronic conductance analysis?

Rangel¹,

Rignanese²,

Olevano³

2015

Beilstein J. Nanotechnol.

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SummaryUsing 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.

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“…To further validate these results, an alternative procedure that would take into account the fluctuations caused by thermal motion would be desirable. A strategy similar to that employed in refs and , namely, classical molecular dynamics with enhanced sampling and a Σ-extended Hückel hamiltonian + NEGF scheme for transport-property calculations, or the strategy employed in ref , which consists of a combination of ab initio molecular dynamics to obtain a statistically relevant sample of configurations and a DFT + NEGF approach to obtain the electrical conductance, would yield conductance histograms more comparable to those obtained experimentally.…”

Section: Resultsmentioning

confidence: 99%

Mechanical Effects on the Electronic Properties of a Biphenyl-Based Molecular Switch

2015

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Using a combination of density functional theory and non-equilibrium Green function calculations, the effect of mechanically stretching a biphenyl-based molecular switch bonded to Au electrodes is studied. Thermodynamic and transport properties of the high and low conducting species are analyzed. A disulfide functionality bridging the aromatic rings is used to switch between the high and low conducting species. The potential of such a system as a molecular device has already been proved [J. Phys. Chem. C 2013, 117, 25724]. Mechanically stretching the molecular junction has major effects on both the thermodynamics of the switching reaction and the conductance ratio between the high and low conducting species involved in the molecular switch. It is also shown that the conductance of each individual species can be modulated by means of an external mechanical force, thus providing a dual switching mechanism for the proposed system.

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Electric conductance of a mechanically strained molecular junction from first principles: Crucial role of structural relaxation and conformation sampling

Cited by 10 publications

References 51 publications

Nanomechanics of Bidentate Thiolate Ligands on Gold Surfaces

Nanomechanics of Bidentate Thiolate Ligands on Gold Surfaces

Can molecular projected density of states (PDOS) be systematically used in electronic conductance analysis?

Mechanical Effects on the Electronic Properties of a Biphenyl-Based Molecular Switch

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