Calculation of semiconductor band structures and defects by the screened exchange density functional

Clark, S. J.; Robertson, John

doi:10.1002/pssb.201046110

Cited by 27 publications

(31 citation statements)

References 90 publications

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“…The latter is discussed here in the paper by Clark and Robertson [75] and their recent papers [76,100,101] and is justifiable as a Generalized Kohn-Sham scheme [97]. In that case, the screening of the exchange is usually done by a Thomas-Fermi exponential screening and the screening length is not arbitrarily chosen but determined by the valence electron density (excluding d-electrons).…”

Section: Band Gap Correctionsmentioning

confidence: 97%

“…Hybrid functionals were discussed by several contributors to the conference [75,77,[86][87][88]. Hybrid functionals essentially mix some Hartree-Fock with LDA or GGA exchange.…”

Section: Band Gap Correctionsmentioning

confidence: 99%

“…This situation for example occurs for the oxygen vacancy in ZnO [73], a defect that was discussed by several contributors at the workshop and has become a sort of benchmark [68,[74][75][76][77][78].…”

Section: Band Gap Correctionsmentioning

confidence: 99%

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Which electronic structure method for the study of defects: A commentary

Lambrecht¹

2010

Physica Status Solidi (b)

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Phone: þ216 368 6120, Fax: þ216 368 4679 A historic perspective is provided to the choice of methodologies for point defects in semiconductors. A summary and commentary on the highlights of the CECAM workshop: ''Which electronic structure method for the study of defects?'' is given, attempting to provide a link between the different contributions. To this purpose different themes running through the compilation are identified and rather than discussing individual contributions one by one, the discussion is focused around these themes. The first theme is the problem of correcting for finite size effects. The second theme is the problem of the underestimate of the band gaps and how to correct for it in defect calculations. The third theme is the self-interaction error of local density approximation (LDA) and its repercussions for polaronic defects. The fourth theme is progress in methods beyond LDA that are becoming applicable to point defects, either for ground states or excited state properties.

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Section: Band Gap Correctionsmentioning

confidence: 97%

“…Hybrid functionals were discussed by several contributors to the conference [75,77,[86][87][88]. Hybrid functionals essentially mix some Hartree-Fock with LDA or GGA exchange.…”

Section: Band Gap Correctionsmentioning

confidence: 99%

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Which electronic structure method for the study of defects: A commentary

Lambrecht¹

2010

Physica Status Solidi (b)

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“…The xOEP total energy is slightly below the LFX total energy, differing by at most 0.16eV for FeO (whose xOEP and LFX band structure is in Figure 1); both of these For the TMOs studied here, antiferromagnetism allows the opening of a gap in the single particle spectrum, although semi-local approximations (LDA/GGA) predict a gap that is too small or zero. The better treatment of self-interaction in hybrid functionals [49,50], the Perdew-Zunger SIC [51], LDA+U [52], or previous EXX calculations [47] all yield improved agreement with experiment.…”

Section: Transition Metal Oxidesmentioning

confidence: 83%

A local Fock-exchange potential in Kohn–Sham equations

Hollins¹,

Clark²,

Refson³

et al. 2016

J. Phys.: Condens. Matter

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Abstract.We derive and employ a local potential to represent the Fock exchange operator in electronic single-particle equations. This local Fock-exchange (LFX) potential is very similar to the exact exchange (EXX) potential in density functional theory (DFT). The practical software implementation of the two potentials (LFX and EXX) yields robust and accurate results for a variety of systems (semiconductors, transition metal oxides) where Hartree Fock and popular approximations of DFT typically fail. This includes examples traditionally considered qualitatively inaccessible to calculations that omit correlation.

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“…sX-LDA includes 100% exact exchange and takes the correlation effect into account by short ranged screening of the exchange potential. It accurately describes the electronic structures of various materials [22,23] and has been widely used in the study of point defects [24][25][26]. In our study of uncorrelated multiple defects, multiple point defects are created in the pristine supercell without artificially rearranging the remaining atomic coordination.…”

Section: Methodsmentioning

confidence: 99%

Correlation and ordering of defects in the formation of conducting nanofilaments

Zhang¹,

Li²,

Shi³

2016

J. Phys. D: Appl. Phys.

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We study the dependence of the formation energies of oxygen and metal induced defects in Ta2O5, TaO2, TaO, TiO2 and Ti4O7 on the chemical potential of electron and atomic constitutes. In the study of single defect, metal induced defects are found to be preferable to oxygen induced defects. This is against the experimental fact of the dominant role of oxygen induced defects in the RS process. A simple multiple defects picture without correlated atomic rearrangement does not cure this problem. The problem is resolved under the correlated multiple defect picture where the multiple defects result in correlated atomic rearrangement and the final products show certain atomic ordering. IntroductionResistive switching (RS) in transition metal oxides (TMOs) has attracted great interests for a possible application in nonvolatile memory devices [1,2] and analog memristors [3][4][5]. Defect redistribution under the switching field is generally considered to play prominent role in the reversible RS [6][7][8]. In simple binary TMOs such as Ta2O5 and TiO2, the agglomeration (segregation) of oxygen vacancies and the subsequent growth (rupture) of the conducting filament is one of the most cited RS mechanisms [6][7][8]. These simple binary TMOs have the advantage of easy fabrication. However, the role of oxygen vacancies in the formation of conducting filaments at an atomic level is less well known. Besides the locally formed conducting path, the resistance can also be switched back and forth by the drift of the charged oxygen vacancies towards or away from one of the two electrodes which modifies the width of the interfacial depletion region and consequently the Schottky contact resistance [9]. Oxygen vacancy induced charge trap can also assist bulk like RS through continuous filling or emptying the traps, whose extent of charge occupation varies the resistance [10]. More complicated correlated TMOs like Pr0.7Ca0.3MnO3 [11], SmNiO3 [12] show metal-insulator transition which accounts for the RS. In these correlated TMOs, the oxygen vacancy coordination environment, which is subject to the driving field either electrically or thermally, modulates the local valence state of transition metal by rearranging the hybridization of transition metal d and oxygen p orbitals. Above mentioned TMOs show RS through effective change of the local oxidation state. Therefore, they are categorized as Redox (Reduction-oxidation) RS TMOs [5]. In this work, we focus on the filament type RS. High performance Ta2O5 based nonvolatile memory device [13] and TiO2 memristor based neuromorphic network [14] have recently been demonstrated. In situ characterization revealed that the conducting filaments in TiO2 and Ta2O5 are composed of Magneli phase Ti4O7 [15] and TaO1-x

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Calculation of semiconductor band structures and defects by the screened exchange density functional

Cited by 27 publications

References 90 publications

Which electronic structure method for the study of defects: A commentary

Which electronic structure method for the study of defects: A commentary

A local Fock-exchange potential in Kohn–Sham equations

Correlation and ordering of defects in the formation of conducting nanofilaments

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