Possible bandgap values of graphene-like ZnO in density functional theory corrected by the Hubbard U term and HSE hybrid functional

2020 ◽  
Vol 22 ◽  
pp. 100756 ◽  
Author(s):  
Asiye Shokri ◽  
Ahmad Yazdani ◽  
Kourosh Rahimi
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Hybrid Functional ◽  
Functional Theory ◽  
Hubbard U

A complete ab initio thermodynamic and kinetic catalogue of the defect chemistry of hematite α-Fe2O3, its cation diffusion, and sample donor dopants

2021 ◽  
Author(s):  
Shehab Shousha ◽  
Sarah Khalil ◽  
Mostafa Youssef
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Defect Formation ◽  
Defect Chemistry ◽  
Cation Diffusion ◽  
Functional Theory ◽  
Migration Barriers ◽  
Hubbard U ◽  
And Migration ◽  
Formation Energies

This paper studies comprehensively the defect chemistry and cation diffusion in α-Fe2O3. Defect formation energies and migration barriers are calculated using density functional theory with a theoretically calibrated Hubbard U...

Hybrid functional calculations of electronic and thermoelectric properties of GaS, GaSe, and GaTe monolayers

2018 ◽  
Vol 20 (45) ◽  
pp. 28575-28582 ◽  
Author(s):  
Bhagwati Prasad Bahuguna ◽  
L. K. Saini ◽  
Rajesh O. Sharma ◽  
Brajesh Tiwari
Keyword(s):  
Density Functional Theory ◽  
Transport Equation ◽  
Thermoelectric Properties ◽  
First Principles ◽  
Density Functional ◽  
Boltzmann Transport Equation ◽  
Boltzmann Transport ◽  
Hybrid Functional ◽  
Functional Theory

We have investigated the structural, electronic and thermoelectric properties of GaS, GaSe and GaTe monolayers based on the first-principles approach by using density functional theory and the semi-classical Boltzmann transport equation.

scholarly journals Designing an active Ta3N5 photocatalyst for H2 and O2 evolution reactions by specific exposed facet engineering: a first-principles study

2020 ◽  
Vol 22 (18) ◽  
pp. 10295-10304 ◽  
Author(s):  
Moussab Harb ◽  
Luigi Cavallo ◽  
Jean-Marie Basset
Keyword(s):  
Density Functional Theory ◽  
Water Splitting ◽  
First Principles ◽  
Density Functional ◽  
O2 Evolution ◽  
Hybrid Functional ◽  
Functional Theory ◽  
Native Defects ◽  
Exposed Facet ◽  
Exposed Facets

The effects of native defects and exposed facets on the thermodynamic stability and photocatalytic characteristics of Ta3N5 for water splitting are studied by applying accurate quantum computations on the basis of density functional theory (DFT) with the range-separated hybrid functional (HSE06).

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>

Density Functional Theory plus Hubbard U Study of the Segregation of Pt to the CeO2–x Grain Boundary

Nano Letters ◽  
2018 ◽  
Vol 18 (3) ◽  
pp. 1668-1677 ◽  
Author(s):  
Guoli Zhou ◽  
Pan Li ◽  
Qingmin Ma ◽  
Zhixue Tian ◽  
Ying Liu
Keyword(s):  
Density Functional Theory ◽  
Grain Boundary ◽  
Density Functional ◽  
Functional Theory ◽  
Hubbard U

Ab Initio Study of Clean and Hydrogen-Saturated Unreconstructed SiC{0001} Surfaces

2007 ◽  
Vol 556-557 ◽  
pp. 493-496 ◽  
Author(s):  
Alexander Mattausch ◽  
T. Dannecker ◽  
Oleg Pankratov
Keyword(s):  
Experimental Data ◽  
Density Functional Theory ◽  
Density Functional ◽  
Surface States ◽  
Correlation Effects ◽  
Ab Initio Study ◽  
Functional Theory ◽  
Hubbard U ◽  
The Impact ◽  
Good Agreement

Using density functional theory, we investigate the 6H-SiC{0001} surfaces in the unreconstructed 1 × 1 and the H-passivated configuration. The strong correlation effects of the dangling bonds at the surface are treated by spin-polarised calculations including the Hubbard-U parameter. We find that the clean surfaces are semiconducting with surface states in good agreement with experimental data. The impact of the Hubbard-U is stronger on the C-terminated face. For the H-passivated surfaces we find resonances in the valence band. The antibonding C−H state is located in the upper part of the bandgap around the ¯􀀀-point.

scholarly journals Computational studies of the thermodynamic properties, and global and reactivity descriptors of fluorescein dye derivatives in acetonitrile using density functional theory

2021 ◽  
pp. 174751982199451
Author(s):  
Juma Mzume Juma ◽  
Said AH Vuai
Keyword(s):  
Density Functional Theory ◽  
Thermodynamic Properties ◽  
Ionization Potential ◽  
Molecular Orbital ◽  
Density Functional ◽  
Energy Gap ◽  
Basis Sets ◽  
Hybrid Functional ◽  
Functional Theory ◽  
Reactivity Descriptors

This work reports density functional theory calculations of the optimized geometries, molecular reactivity, energy gap, and thermodynamic properties of molecular dyes fluorescein (FS), fluorescein attached with methoxy (FSO), fluorescein attached with amine (FSA), fluorescein attached with methane (FSM), fluorescein attached with ethene (FSE), and fluorescein attached with thiophene (FST) using the hybrid functional B3LYP and 6-311G basis sets. When donating groups are attached to the molecular dye, the bond lengths are slightly decreased which is important for easy transfer of electron from donating to the accepting group. For all dyes, highest occupied molecular orbital/lowest occupied molecular orbital analysis results in positive outcomes upon electron injection to semiconductors and subsequent dye regeneration by the electrolyte. The ionization potential increases with increasing conjugation; therefore, the molecular dye attached to thiophene has the highest ionization potential. Meanwhile, a donating group with increased conjugation results in low electron affinity.

scholarly journals Comparative Analysis of DFTU, ACBN0, and Hybrid Functionals on the Spin Density of YTiO3 and SrRuO3+

2021 ◽  
Vol 11 (2) ◽  
pp. 616
Author(s):  
Francesca Menescardi ◽  
Davide Ceresoli
Keyword(s):  
Density Functional Theory ◽  
Quantum Theory ◽  
Spin Density ◽  
Density Functional ◽  
Functional Theory ◽  
Atomic Orbitals ◽  
Hubbard U ◽  
Density Map ◽  
Hybrid Functionals ◽  
Standard Density

We present a quantitative analysis of the theoretical spin density map of two ferromagnetic perovskites, YTiO3 and SrRuO3. We calculated the spin density using the standard density functional theory (DFT)+U method, where the Hubbard U correction is applied to the Ti and Ru ions, and with the pseudo-hybrid ACBN0 method, where the Hubbard U parameters are determined self-consistently. The ACBN0 calculations yielded a large value of the Hubbard U of the oxygen 2p orbitals. We also used the screened hybrid HSE06 functional, which is widely used to describe the electronic structure of oxides. We used the Quantum Theory of Atoms in Molecules (QTAIM) theory and integrated the spin density in the atomic basins instead of projecting on atomic orbitals. This way, our results can be compared to experimental reports as well as to other DFT calculations.

scholarly journals Comprehensive Density Functional Theory Studies of Vibrational Spectra of Carbonates

Nanomaterials ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 2275
Author(s):  
Yurii N. Zhuravlev ◽  
Victor V. Atuchin
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Predictive Power ◽  
Hybrid Functional ◽  
Program Code ◽  
Functional Theory ◽  
Carbonate Solutions ◽  
The Density Functional Theory ◽  
Bending Mode ◽  
Cation Radius

Within the framework of the density functional theory (DFT) and the hybrid functional B3LYP by means of the CRYSTAL17 program code, the wavenumbers and intensities of normal oscillations of MgCO3, CaCO3, ZnCO3, CdCO3 in the structure of calcite; CaMg(CO3)2, CdMg(CO3)2, CaMn(CO3)2, CaZn(CO3)2 in the structure of dolomite; BaMg(CO3)2 in the structure of the norsethite type; and CaCO3, SrCO3, BaCO3, and PbCO3 in the structure of aragonite were calculated. Infrared absorption and Raman spectra were compared with the known experimental data of synthetic and natural crystals. For lattice and intramolecular modes, linear dependences on the radius and mass of the metal cation are established. The obtained dependences have predictive power and can be used to study solid carbonate solutions. For trigonal and orthorhombic carbonates, the linear dependence of wavenumbers on the cation radius RM (or M–O distance) is established for the infrared in-plane bending mode: 786.2–65.88·RM and Raman in-plane stretching mode: 768.5–53.24·RM, with a correlation coefficient of 0.87.

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