scholarly journals The screening effects of the screened exchange hybrid functional in surface systems: A case study on the CO/Pt(111) problem

AIP Advances ◽  
2016 ◽  
Vol 6 (6) ◽  
pp. 065309 ◽  
Author(s):  
H. Li ◽  
R. Gillen ◽  
J. Robertson
Keyword(s):  
Hybrid Functional ◽  
Screened Exchange

Calibration sets and the accuracy of vibrational scaling factors: A case study with the X3LYP hybrid functional

2010 ◽  
Vol 133 (11) ◽  
pp. 114109 ◽  
Author(s):  
Filipe Teixeira ◽  
André Melo ◽  
M. Natália D. S. Cordeiro
Keyword(s):  
Hybrid Functional ◽  
Scaling Factors ◽  
Calibration Sets

Screened exchange hybrid density functional for accurate and efficient structures and interaction energies

2016 ◽  
Vol 18 (23) ◽  
pp. 15519-15523 ◽  
Author(s):  
Jan Gerit Brandenburg ◽  
Eike Caldeweyher ◽  
Stefan Grimme
Keyword(s):  
Density Functional ◽  
Interaction Energies ◽  
Computationally Efficient ◽  
Hybrid Functional ◽  
Screened Exchange ◽  
Hybrid Density Functional

HSE-3c: a computationally efficient and numerically robust screened hybrid functional that can be applied to periodic small gap systems.

The Meaning of Airspace Sovereignty Today – A Case Study on Demilitarisation and Functional Airspace Blocks

2017 ◽  
Vol 86 (1) ◽  
pp. 91-117
Author(s):  
Sia Spiliopoulou Åkermark
Keyword(s):  
International Cooperation ◽  
Hybrid Mode ◽  
Hybrid Functional ◽  
International Enterprise ◽  
The North ◽  
Legal Obligations ◽  
Democratic Control ◽  
Regional Agreements

As a result of the eu Single European Sky directives, European states adopted regional agreements on functional airspace blocks. The Agreement on the North European Functional Airspace Block (nefab) was signed in 2012 by Estonia, Finland, Latvia and Norway. The nature of the agreement is mixed and involves civil as well as military actors. nefab seems to operate in practice in a hybrid mode, sometimes looking like a private international enterprise and sometimes more like a public international organisation. Does the highly technical nature of the agreement keep issues of political and legal relevance outside the range of democratic control? To what extent can such hybrid, functional, technical regimes of international cooperation affect the understandings and the exercise of sovereignty, and what is the effect of the NEFAB-regime on older legal obligations such as the demilitarisation and neutralisation regime of the Åland Islands?

scholarly journals The GW Miracle in Many-Body Perturbation Theory for the Ionization Potential of Molecules

2021 ◽  
Vol 9 ◽  
Author(s):  
Fabien Bruneval ◽  
Nike Dattani ◽  
Michiel J. van Setten
Keyword(s):  
Perturbation Theory ◽  
Ionization Potential ◽  
Positive Impact ◽  
Second Order ◽  
Many Body ◽  
Hybrid Functional ◽  
Hartree Fock ◽  
Screened Exchange ◽  
Many Body Perturbation Theory ◽  
High Level

We use the GW100 benchmark set to systematically judge the quality of several perturbation theories against high-level quantum chemistry methods. First of all, we revisit the reference CCSD(T) ionization potentials for this popular benchmark set and establish a revised set of CCSD(T) results. Then, for all of these 100 molecules, we calculate the HOMO energy within second and third-order perturbation theory (PT2 and PT3), and, GW as post-Hartree-Fock methods. We found GW to be the most accurate of these three approximations for the ionization potential, by far. Going beyond GW by adding more diagrams is a tedious and dangerous activity: We tried to complement GW with second-order exchange (SOX), with second-order screened exchange (SOSEX), with interacting electron-hole pairs (WTDHF), and with a GW density-matrix (γGW). Only the γGW result has a positive impact. Finally using an improved hybrid functional for the non-interacting Green’s function, considering it as a cheap way to approximate self-consistency, the accuracy of the simplest GW approximation improves even more. We conclude that GW is a miracle: Its subtle balance makes GW both accurate and fast.

First-principles study of Oxygen deficiency in rutile Titanium Dioxide

2011 ◽  
Vol 1352 ◽  
Author(s):  
Hsin-Yi Lee ◽  
Stewart J. Clark ◽  
John Robertson
Keyword(s):  
Oxygen Vacancy ◽  
Band Gap ◽  
Defect Formation ◽  
Chemical Potential ◽  
Oxygen Deficiency ◽  
Energy Levels ◽  
Hybrid Functional ◽  
Charge Densities ◽  
Screened Exchange ◽  
Rutile Titanium Dioxide

ABSTRACTThe energy levels of the different charge states of an oxygen vacancy and titanium interstitial in rutile TiO2 were calculated using the screened exchange (sX) hybrid functional [1]. The sX method gives 3.1 eV for the band gap of rutile TiO2, which is close to the experimental value. We report the defect formation energy of the oxygen deficient structure. It is found that the defect formation energies, for the neutral charge state, of oxygen vacancy and titanium interstitial are quite similar, 2.40 eV and 2.45 eV respectively, for an oxygen chemical potential of the O-poor condition. The similar size of these two calculated energies indicates that both are a cause of oxygen deficiency, as observed experimentally [2]. The transition energy level of oxygen vacancy lies within the band gap, corresponding to the electrons located at adjacent titanium sites. The sX method gives a correct description of the localization of defect charge densities, which is not the case for GGA [3-6].

Ab-Initio Modeling of the Resistance Switching Mechanism in RRAM Devices: Case Study of Hafnium Oxide (HfO2)

2012 ◽  
Vol 1430 ◽  
Author(s):  
Dan Duncan ◽  
Blanka Magyari-Kope ◽  
Yoshio Nishi
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Hafnium Oxide ◽  
Density Functional ◽  
Hybrid Functional ◽  
Functional Theory ◽  
Electronic Interactions ◽  
Hybrid Functionals ◽  
Electronic And Structural Properties

ABSTRACTThe structures and energies of stoichiometric and oxygen-deficient monoclinic HfO2 were calculated using density functional theory. The electronic interactions in HfO2 were calculated using the LDA+U and GGA+U formalisms, where on-site Coulomb corrections were applied to the 5d electrons of hafnium (Ud) and the 2p electrons of oxygen (Up). Properties calculated using these techniques are compared to results obtained from LDA, GGA, hybrid functionals, and experiment. Ultimately, we show that LDA+Ud+Up and GGA+Ud+Up calculations of HfO2’s electronic and structural properties achieve a level of accuracy on par with much more computationally demanding hybrid functional techniques, such as PBE0 and HSE06.

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