Fundamental gap of molecular crystals via constrained density functional theory

Droghetti, Andrea; Rungger, Ivan; Pemmaraju, C. D.; Sanvito, Stefano

doi:10.1103/physrevb.93.195208

Cited by 16 publications

(14 citation statements)

References 63 publications

(84 reference statements)

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“…The most widely encountered of these is the many-electron self-interaction error (SIE) 6 , or delocalization 12 error, which is manifested as a spurious curvature in the total-energy profile of a system with respect to its total electron number 13 . The SIE contributes to inaccuracies in insulating band gaps 14 , charge-transfer energies 15,16 , activation barriers 17 , binding and formation energies, as well as in spin-densities and their moments. While the nature of SIE is well understood, it remains persistently challenging to reliably avoid its introduction using approximate xc functionals of a computationally tractable, explicit analytical form, even if exact exchange is incorporated (see, e.g., the B3LYP curve in Fig.…”

Section: Introductionmentioning

confidence: 99%

A self-consistent ground-state formulation of the first-principles Hubbard U parameter validated on one-electron self-interaction error

Moynihan,

Teobaldi,

O'Regan

2017

Preprint

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In electronic structure methods based on the correction of approximate density-functional theory (DFT) for systematic inaccuracies, Hubbard U parameters may be used to quantify and amend the self-interaction errors ascribed to selected subspaces. Here, in order to enable the accurate, computationally convenient calculation of U by means of DFT algorithms that locate the ground-state by direct total-energy minimization, we introduce a reformulation of the successful linear-response method for U in terms of the fully-relaxed constrained ground-state density. Defining U as an implicit functional of the ground-state density implies the comparability of DFT + Hubbard U (DFT+U ) total-energies, and related properties, as external parameters such as ionic positions are varied together with their corresponding first-principles U values. Our approach provides a framework in which to address the partially unresolved question of self-consistency over U , for which plausible schemes have been proposed, and to precisely define the energy associated with subspace many-body self-interaction error. We demonstrate that DFT+U precisely corrects the total energy for self-interaction error under ideal conditions, but only if a simple self-consistency condition is applied. Such parameters also promote to first-principles a recently proposed DFT+U based method for enforcing Koopmans' theorem.

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Section: Introductionmentioning

confidence: 99%

A self-consistent ground-state formulation of the first-principles Hubbard U parameter validated on one-electron self-interaction error

Moynihan,

Teobaldi,

O'Regan

2017

Preprint

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show abstract

“…Table IV Putting molecules in a solvent, for example in molecular crystal, gap renormalizes due to electronic polarization effects. [53][54][55] Within the non-local vdW-DF-cx functional, the relaxed lattice parameters of TCNQ crystal are: a=8. Fig.…”

Section: First-principles Dft and Gw Calculationsmentioning

confidence: 99%

First-Principles Calculation of Charge Transfer at the Silicon–Organic Interface

2017

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Organic dopants are frequently used to surface-dope inorganic semiconductors. The resulted hybrid inorganic-organic materials have a crucial role in advanced functional materials and semiconductor devices. In this article, we study charge transfer at hybrid silicon-molecule interfaces theoretically. The idea is to filter out the best molecular acceptors to dope silicon with hole densities as high as 10 13 cm -2 . Here, we use a combinatorial algorithm merging chemical hardness method and first-principles DFT and GW calculations. We start by using the chemical hardness method which is simple and fast to narrow down our search for molecular dopants. Then, for the most optimistic candidates, we perform first-principles DFT calculations and discuss the necessity of GW corrections. This screening approach is quite general and applicable to other hybrid interfaces.

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“…Because of that, we also use constrained-DFT (c-DFT) [44][45][46][47] with the local spin density approximation for the exchange correlation potential as a complementary approach. In fact it has been demonstrated that c-DFT generally returns quite accurate results for the energies of the frontier orbitals of molecules inside crystals and clusters 48,49 . Specifically, the energy of the lowest unoccupied molecular orbital (LUMO) of Alq The G 0 W 0 DOS is presented in Fig.…”

Section: A Electronic Propertiesmentioning

confidence: 99%

Oxygen doping and polaron magnetic coupling in Alq$_3$ films

Droghetti

2021

Preprint

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The understanding of the Physics underlying the performances of spin-valve devices comprising organic semiconductors is still incomplete. According to some recent models, spin transport takes place in an impurity band inside the fundamental gap of the organic semiconductor. This seems to be confirmed by recent experiments performed with La0.7Sr0.3MnO3/Alq3/AlOx/Co devices. The reported results suggest a possible correlation between the magnetoresistance and the variable oxygen doping in the Alq3 spacer. In this paper we investigate the electronic and magnetic properties of O2 molecules and ions in Alq3 films by means of first-principles calculations to establish whether oxygen plays any important role for spin transport in La0.7Sr0.3MnO3/Alq3/AlOx/Co devices. The conclusion is that it does not. In fact, we show that O2 molecules do not form an impurity band and there is no magnetic interaction between them. In contrast, we suggest that spin-transport may be enabled by the direct exchange coupling between Alq − 3 ions.

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Fundamental gap of molecular crystals via constrained density functional theory

Cited by 16 publications

References 63 publications

A self-consistent ground-state formulation of the first-principles Hubbard U parameter validated on one-electron self-interaction error

A self-consistent ground-state formulation of the first-principles Hubbard U parameter validated on one-electron self-interaction error

First-Principles Calculation of Charge Transfer at the Silicon–Organic Interface

Oxygen doping and polaron magnetic coupling in Alq$_3$ films

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