Constrained-DFT method for accurate energy-level alignment of metal/molecule interfaces

Souza, A. M.; Rungger, Ivan; Pemmaraju, C. D.; Schwingenschloegl, Udo; Sanvito, Stefano

doi:10.1103/physrevb.88.165112

Cited by 63 publications

(92 citation statements)

References 55 publications

(97 reference statements)

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“…61 Hence the classical models shown in eqn (3) and (4) are effectively parameter-free when based on the CDFT value for d 0 .…”

Section: Constrained Density Functional Theorymentioning

confidence: 99%

“…Therefore, different alternative approaches and corrections have been proposed to improve the description of the energy level alignment, for instance, corrections for self-interaction (SI) errors, 13,58 scissor operator (SCO) schemes 35,48,52,59,60 and constrained-DFT (CDFT). 61 In the present work we investigate, by means of total energy DFT and quantum transport calculations, the stability and conductivity of thiol and thiolate molecular junctions. We compare the results for the two systems and we relate them to experimental data.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2014

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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.

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“…61 Hence the classical models shown in eqn (3) and (4) are effectively parameter-free when based on the CDFT value for d 0 .…”

Section: Constrained Density Functional Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2014

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“…2(b), the supercell is no longer charge neutral, and the image-image interaction of the extra charge due to the finite size of the supercell becomes significant. However, we note that in a semi-infinite system, the extra s l charge on the molecule will be completely compensated by the metal surface charge of opposite sign and a dipole is formed near the surface [28]. In practice, we mimic this situation in our calculation using a finite Au slab.…”

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confidence: 99%

The energy level alignment at metal–molecule interfaces using Wannier–Koopmans method

Liu

Neaton

et al. 2016

Applied Physics Letters

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We apply a newly developed Wannier-Koopmans method (WKM), based on density functional theory (DFT), to calculate the electronic energy level alignment at an interface between a molecule and metal substrate. We consider two systems: benzenediamine on Au (111), and a bipyridineAu molecular junction. The WKM calculated level alignment agrees well with the experimental measurements where available, as well as previous GW and DFT+Σ results. Our results suggest that the WKM is a general approach that can be used to correct DFT eigenvalue errors, not only in bulk semiconductors and isolated molecules, but also hybrid interfaces. * lwwang@lbl.gov [6,7] is often used as the starting point in approaching this problem. Although DFT with common approximate exchange-correlation functionals can in general be accurate for total energy related properties such as geometries and forces, there is no fundamental theorem in DFT that guarantees the validity of Kohn-Sham (KS) eigenvalues as quasiparticle energies [8], at least other than the highest occupied KS eigenvalue. In practice, with local or semi-local functionals, KS eigenvalues can differ from quasiparticle energies by a few eV's,

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“…CDFT has been used successfully for problems concerning molecular systems, for instance, for describing long-range charge-transfer excitations between molecules [36,39,40]. Moreover, in some recent works [41][42][43], it has been employed for determining the energy level alignment at hybrid organicinorganic interfaces. The results have been promising, showing that the method can capture image charge and polarization effects.…”

Section: Introductionmentioning

confidence: 99%

Fundamental gap of molecular crystals via constrained density functional theory

et al. 2016

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The energy gap of a molecular crystal is one of the most important properties since it determines the crystal charge transport when the material is utilized in electronic devices. This is, however, a quantity difficult to calculate and standard theoretical approaches based on density functional theory (DFT) have proven unable to provide accurate estimates. In fact, besides the well-known band-gap problem, DFT completely fails in capturing the fundamental gap reduction occurring when molecules are packed in a crystal structures. The failure has to be associated with the inability of describing the electronic polarization and the real space localization of the charged states. Here we describe a scheme based on constrained DFT, which can improve upon the shortcomings of standard DFT. The method is applied to the benzene crystal, where we show that accurate results can be achieved for both the band gap and also the energy level alignment.

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Constrained-DFT method for accurate energy-level alignment of metal/molecule interfaces

Cited by 63 publications

References 55 publications

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

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

The energy level alignment at metal–molecule interfaces using Wannier–Koopmans method

Fundamental gap of molecular crystals via constrained density functional theory

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