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.

The role of exchange–correlation functional on the description of multiferroic properties using density functional theory: the ATiO3 (A = Mn, Fe, Ni) case study

RSC Advances ◽  
2016 ◽  
Vol 6 (103) ◽  
pp. 101216-101225 ◽  
Author(s):  
Renan Augusto Pontes Ribeiro ◽  
Sergio Ricardo de Lazaro ◽  
Carlo Gatti
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Multiferroic Properties ◽  
Exchange Correlation

In this study, ab initio density functional theory calculations were performed on ATiO3 (A = Mn, Fe, Ni) materials for multiferroic applications.

scholarly journals Exact Generalized Kohn-Sham Theory for Hybrid Functionals

2019 ◽  
Author(s):  
Rachel Garrick ◽  
Amir Natan ◽  
Tim Gould ◽  
Leeor Kronik
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
State Density ◽  
Hybrid Functional ◽  
Functional Theory ◽  
Hybrid Functionals ◽  
The Many ◽  
Ground State Density ◽  
Equivalent Description

p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; line-height: 18.0px; font: 15.8px Helvetica; color: #000000; -webkit-text-stroke: #000000; background-color: #ffffff} span.s1 {font-kerning: none} span.s2 {font-kerning: none; color: #000000} <p>Hybrid functionals have proven to be of immense practical value in density functional theory calculations. While they are often thought to be a heuristic construct, it has been established that this is in fact not the case. Here, we present a rigorous and formally exact generalized Kohn-Sham (GKS) density functional theory of hybrid functionals, in which exact remainder exchange-correlation potentials combine with a fraction of Fock exchange to produce the correct ground state density. Specifically, we generalize the well-known adiabatic con- nection theorem to the case of exact hybrid functional theory and use it to provide a rigorous distinction between multiplicative exchange and correlation components. We examine the exact theory by inverting reference electron densities to obtain exact GKS potentials for hybrid functionals, showing that an equivalent description of the many-electron problem is obtained with any arbitrary global fraction of Fock exchange. We establish the dependence of these exact components on the fraction of Fock exchange and use the observed trends to shed new light on the results of approximate hybrid functional calculations.</p>

scholarly journals Exact Generalized Kohn-Sham Theory for Hybrid Functionals

2020 ◽  
Author(s):  
Rachel Garrick ◽  
Amir Natan ◽  
Tim Gould ◽  
Leeor Kronik
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Formal Theory ◽  
Density Functional Theory Calculations ◽  
State Density ◽  
Hybrid Functional ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Hybrid Functionals ◽  
The Many

Hybrid functionals have proven to be of immense practical value in density functional theory calculations. While they are often thought to be a heuristic construct, it has been established that this is in fact not the case. Here, we present a rigorous and formally exact analysis of generalized Kohn-Sham (GKS) density functional theory of hybrid functionals, in which exact remainder exchange-correlation potentials combine with a fraction of Fock exchange to produce the correct ground state density. First, we extend formal GKS theory by proving a generalized adiabatic connection theorem. We then use this extension to derive two different definitions for a rigorous distinction between multiplicative exchange and correlation components - one new and one previously postulated. We examine their density-scaling behavior and discuss their similarities and differences. We then present a new algorithm for obtaining exact GKS potentials by inversion of accurate reference electron densities and employ this algorithm to obtain exact potentials for simple atoms and ions. We establish that an equivalent description of the many-electron problem is indeed obtained with any arbitrary global fraction of Fock exchange and we rationalize the Fock-fraction dependence of the computed remainder exchange-correlation potentials in terms of the new formal theory. Finally, we use the exact theoretical framework and numerical results to shed light on the exchange-correlation potential used in approximate hybrid functional calculations and to assess the consequences of different choices of fractional exchange.<br><br>

scholarly journals Benchmark study of the performance of density functional theory for reduction potentials of vanadium compounds

2020 ◽  
pp. 14-21
Author(s):  
Samat Tussupbayev ◽  
Gulnar Kudaibergenova
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Vanadium Redox Flow Battery ◽  
Hybrid Functional ◽  
Vanadium Compounds ◽  
Functional Theory ◽  
Hartree Fock ◽  
Benchmark Study ◽  
Reduction Potentials ◽  
Hybrid Functionals

A systematic benchmark study was performed for the first time to investigate the performance of density functional theory for calculation of reduction potentials of vanadium compounds. Six density functionals of different types were selected for testing: local OLYP and M06L, global hybrid O3LYP and B3LYP, as well as, meta-hybrid functionals TPSSh and M06. Local and hybrid functionals with a relatively high contribution of Hartree-Fock exchange showed unsatisfactory results. In particular, the widely used hybrid functional B3LYP for the transformation VIII→VII occurring in the vanadium redox flow battery yields a negative value of the standard potential instead of a positive one. Among the tested functionals the smallest deviation from the experimental data provides the meta-hybrid functional TPSSh with a 10% contribution of the Hartree-Fock exchange. The computational protocol to calculate redox potentials of vanadium compounds is suggested.

scholarly journals Electronic properties of several two dimensional halides from ab initio calculations

2019 ◽  
Vol 10 ◽  
pp. 823-832 ◽  
Author(s):  
Mohamed Barhoumi ◽  
Ali Abboud ◽  
Lamjed Debbichi ◽  
Moncef Said ◽  
Torbjörn Björkman ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Electric Field ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Electronic Properties ◽  
Density Functional ◽  
Two Dimensional ◽  
Hybrid Functional ◽  
Functional Theory ◽  
Phonon Spectra

Using density functional theory, we study the electronic properties of several halide monolayers. We show that their electronic bandgaps, as obtained with the HSE hybrid functional, range between 3.0 and 7.5 eV and that their phonon spectra are dynamically stable. Additionally, we show that under an external electric field some of these systems exhibit a semiconductor-to-metal transition.

scholarly journals Exact Generalized Kohn-Sham Theory for Hybrid Functionals

2020 ◽  
Author(s):  
Rachel Garrick ◽  
Amir Natan ◽  
Tim Gould ◽  
Leeor Kronik
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Formal Theory ◽  
Density Functional Theory Calculations ◽  
State Density ◽  
Hybrid Functional ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Hybrid Functionals ◽  
The Many

Hybrid functionals have proven to be of immense practical value in density functional theory calculations. While they are often thought to be a heuristic construct, it has been established that this is in fact not the case. Here, we present a rigorous and formally exact analysis of generalized Kohn-Sham (GKS) density functional theory of hybrid functionals, in which exact remainder exchange-correlation potentials combine with a fraction of Fock exchange to produce the correct ground state density. First, we extend formal GKS theory by proving a generalized adiabatic connection theorem. We then use this extension to derive two different definitions for a rigorous distinction between multiplicative exchange and correlation components - one new and one previously postulated. We examine their density-scaling behavior and discuss their similarities and differences. We then present a new algorithm for obtaining exact GKS potentials by inversion of accurate reference electron densities and employ this algorithm to obtain exact potentials for simple atoms and ions. We establish that an equivalent description of the many-electron problem is indeed obtained with any arbitrary global fraction of Fock exchange and we rationalize the Fock-fraction dependence of the computed remainder exchange-correlation potentials in terms of the new formal theory. Finally, we use the exact theoretical framework and numerical results to shed light on the exchange-correlation potential used in approximate hybrid functional calculations and to assess the consequences of different choices of fractional exchange.<br><br>

scholarly journals Exact Generalized Kohn-Sham Theory for Hybrid Functionals

2020 ◽  
Author(s):  
Rachel Garrick ◽  
Amir Natan ◽  
Tim Gould ◽  
Leeor Kronik
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Formal Theory ◽  
Density Functional Theory Calculations ◽  
State Density ◽  
Hybrid Functional ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Hybrid Functionals ◽  
The Many

<div>Hybrid functionals have proven to be of immense practical value in density functional theory calculations.</div><div>While they are often thought to be a heuristic construct, it has been established that this is in fact not the</div><div>case. Here, we present a rigorous and formally exact generalized Kohn-Sham (GKS) density functional theory</div><div>of hybrid functionals, in which exact remainder exchange-correlation potentials combine with a fraction of</div><div>Fock exchange to produce the correct ground state density. First, we extend formal GKS theory by proving a</div><div>generalized adiabatic connection theorem. We then use this extension to derive two different definitions for a</div><div>rigorous distinction between multiplicative exchange and correlation components - one new and one previously</div><div>postulated. We examine their density-scaling behavior and discuss their similarities and differences. We then</div><div>present a new algorithm for obtaining exact GKS potentials by inversion of accurate reference electron densities</div><div>and employ this algorithm to obtain exact potentials for simple atoms and ions. We establish that an equivalent</div><div>description of the many-electron problem is indeed obtained with any arbitrary global fraction of Fock exchange</div><div>and we rationalize the Fock-fraction dependence of the computed remainder exchange-correlation potentials in</div><div>terms of the new formal theory. Finally, we use the exact theoretical framework and numerical results to shed</div><div>light on the exchange-correlation potential used in approximate hybrid functional calculations and to assess the</div><div>consequences of different choices of fractional exchange.</div>

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