scholarly journals Extensive Benchmarking of DFT+U Calculations for Predicting Band Gaps

2021 ◽  
Vol 11 (5) ◽  
pp. 2395 ◽  
Author(s):  
Nicole E. Kirchner-Hall ◽  
Wayne Zhao ◽  
Yihuang Xiong ◽  
Iurii Timrov ◽  
Ismaila Dabo
Keyword(s):  
Total Energy ◽  
Band Gap ◽  
Density Functional ◽  
Practical Importance ◽  
Computational Cost ◽  
Potential Method ◽  
Band Gaps ◽  
Edge States ◽  
Piecewise Linearity ◽  
Hubbard U

Accurate computational predictions of band gaps are of practical importance to the modeling and development of semiconductor technologies, such as (opto)electronic devices and photoelectrochemical cells. Among available electronic-structure methods, density-functional theory (DFT) with the Hubbard U correction (DFT+U) applied to band edge states is a computationally tractable approach to improve the accuracy of band gap predictions beyond that of DFT calculations based on (semi)local functionals. At variance with DFT approximations, which are not intended to describe optical band gaps and other excited-state properties, DFT+U can be interpreted as an approximate spectral-potential method when U is determined by imposing the piecewise linearity of the total energy with respect to electronic occupations in the Hubbard manifold (thus removing self-interaction errors in this subspace), thereby providing a (heuristic) justification for using DFT+U to predict band gaps. However, it is still frequent in the literature to determine the Hubbard U parameters semiempirically by tuning their values to reproduce experimental band gaps, which ultimately alters the description of other total-energy characteristics. Here, we present an extensive assessment of DFT+U band gaps computed using self-consistent ab initio U parameters obtained from density-functional perturbation theory to impose the aforementioned piecewise linearity of the total energy. The study is carried out on 20 compounds containing transition-metal or p-block (group III-IV) elements, including oxides, nitrides, sulfides, oxynitrides, and oxysulfides. By comparing DFT+U results obtained using nonorthogonalized and orthogonalized atomic orbitals as Hubbard projectors, we find that the predicted band gaps are extremely sensitive to the type of projector functions and that the orthogonalized projectors give the most accurate band gaps, in satisfactory agreement with experimental data. This work demonstrates that DFT+U may serve as a useful method for high-throughput workflows that require reliable band gap predictions at moderate computational cost.

Structural and Electronic Properties of Oxygen Vacancies in Monoclinic HfO2

2007 ◽  
Vol 996 ◽  
Author(s):  
Peter Broqvist ◽  
Alfredo Pasquarello
Keyword(s):  
Oxygen Vacancy ◽  
Optical Absorption ◽  
Total Energy ◽  
Band Gap ◽  
Electronic Properties ◽  
Density Functional ◽  
Oxygen Vacancies ◽  
Structural And Electronic Properties ◽  
Defect Levels ◽  
Hybrid Density Functional

AbstractWe study structural and electronic properties of the oxygen vacancy in monoclinic HfO2 for five different charge states. We use a hybrid density functional to accurately reproduce the experimental band gap. To compare with measured defect levels, we determine total-energy differences appropriate to the considered experiments. Our results show that the oxygen vacancy can consistently account for the defect levels observed in optical absorption, direct electron injection, and trap-assisted conduction experiments.

Non-Dirac Chern insulators with large band gaps and spin-polarized edge states

Nanoscale ◽  
2018 ◽  
Vol 10 (18) ◽  
pp. 8569-8577 ◽  
Author(s):  
Y. Xue ◽  
J. Y. Zhang ◽  
B. Zhao ◽  
X. Y. Wei ◽  
Z. Q. Yang
Keyword(s):  
Band Gap ◽  
Band Gaps ◽  
Edge States ◽  
Half Metallic ◽  
Spin Polarized ◽  
Chern Insulators

A non-Dirac Chern insulator with a large band gap (244 meV) and half-metallic edge states was realized in a PbC/MnSe heterostructure.

Theoretical Investigation on Electronic Properties of ZnO Crystals Using DFT-Based Calculation Method

2015 ◽  
Vol 1112 ◽  
pp. 41-44 ◽  
Author(s):  
Yudi Darma ◽  
Freddy Giovanni Setiawan ◽  
Muhammad Aziz Majidi ◽  
Andrivo Rusydi
Keyword(s):  
Band Gap ◽  
Valence Band ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Valence Band Maximum ◽  
Band Gaps ◽  
Generalized Gradient ◽  
Strong Electron ◽  
Electronic Band ◽  
Rocksalt Structure

We study the electronic band structure and density of states (DOS) on ZnO material in various crystal structures : wurtzite (W), zincblende (ZB), and rocksalt (RS) phases. Calculations are based on Density Functional Theory (DFT) with Generalized Gradient Approximation (GGA) for exchange-correlation functional and Hubbard correction to consider the strong electron correlations in 3d orbitals. After structural optimization, GGA results show that wurtzite and zincblende structures have a direct band gap of 0.749 eV and 0.637 eV, respectively, whereas rocksalt structure has an indirect band gap of 0.817 eV. Symmetrical shape of total DOS for spin up and spin down electrons indicates a zero total magnetic moment. For all ZnO structures, the upper valence band is formed by hybridization among O 2p and Zn 3d orbitals, while lower valence and conduction band are primarily filled by O 2s and Zn 4s, respectively. The GGA+U approach is found to improve the calculated band gaps and correct the position of Zn 3d state below Valence Band Maximum (VBM). From GGA+U, the band gaps for W-ZnO, ZB-ZnO, and RS-ZnO are 1.12 eV, 1.00 eV, and 1.11 eV, respectively.

scholarly journals Predicting band gaps of semiconductors with quantum chemistry

2020 ◽  
Vol 246 ◽  
pp. 00006
Author(s):  
Anneke Dittmer
Keyword(s):  
Density Functional Theory ◽  
Quantum Chemistry ◽  
Band Gap ◽  
Organic Semiconductors ◽  
Density Functional ◽  
Band Gaps ◽  
Coupled Cluster ◽  
Functional Theory ◽  
Coupled Cluster Theory ◽  
Electrostatic Embedding

The following article gives a brief introduction to quantum chemistry and its application to the prediction of band gaps of inorganic and organic semiconductors. Two important quantum chemistry concepts —Density Functional Theory (DFT) and Coupled Cluster Theory (CC)— are shortly explained. These two concepts are used to calculate the optical and the transport band gap of a set of semiconductors modelled with an electrostatic embedding approach.

scholarly journals Band gaps of crystalline solids from Wannier-localization–based optimal tuning of a screened range-separated hybrid functional

2021 ◽  
Vol 118 (34) ◽  
pp. e2104556118 ◽  
Author(s):  
Dahvyd Wing ◽  
Guy Ohad ◽  
Jonah B. Haber ◽  
Marina R. Filip ◽  
Stephen E. Gant ◽  
...  
Keyword(s):  
Band Gap ◽  
Density Functional ◽  
Absolute Error ◽  
Band Gaps ◽  
Crystalline Solid ◽  
Hybrid Functional ◽  
Fundamental Band ◽  
Optimal Tuning ◽  
Quantitative Accuracy ◽  
Occupied State

Accurate prediction of fundamental band gaps of crystalline solid-state systems entirely within density functional theory is a long-standing challenge. Here, we present a simple and inexpensive method that achieves this by means of nonempirical optimal tuning of the parameters of a screened range-separated hybrid functional. The tuning involves the enforcement of an ansatz that generalizes the ionization potential theorem to the removal of an electron from an occupied state described by a localized Wannier function in a modestly sized supercell calculation. The method is benchmarked against experiment for a set of systems ranging from narrow band-gap semiconductors to large band-gap insulators, spanning a range of fundamental band gaps from 0.2 to 14.2 electronvolts (eV), and is found to yield quantitative accuracy across the board, with a mean absolute error of ∼0.1 eV and a maximal error of ∼0.2 eV.

scholarly journals A band-gap database for semiconducting inorganic materials calculated with hybrid functional

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Sangtae Kim ◽  
Miso Lee ◽  
Changho Hong ◽  
Youngchae Yoon ◽  
Hyungmin An ◽  
...  
Keyword(s):  
Band Gap ◽  
Density Functional ◽  
Magnetic Ordering ◽  
Density Functional Theory Calculations ◽  
Inorganic Materials ◽  
Band Gaps ◽  
Device Performance ◽  
Photovoltaic Devices ◽  
Hybrid Functional ◽  
Functional Theory

Abstract Semiconducting inorganic materials with band gaps ranging between 0 and 5 eV constitute major components in electronic, optoelectronic and photovoltaic devices. Since the band gap is a primary material property that affects the device performance, large band-gap databases are useful in selecting optimal materials in each application. While there exist several band-gap databases that are theoretically compiled by density-functional-theory calculations, they suffer from computational limitations such as band-gap underestimation and metastable magnetism. In this data descriptor, we present a computational database of band gaps for 10,481 materials compiled by applying a hybrid functional and considering the stable magnetic ordering. For benchmark materials, the root-mean-square error in reference to experimental data is 0.36 eV, significantly smaller than 0.75–1.05 eV in the existing databases. Furthermore, we identify many small-gap materials that are misclassified as metals in other databases. By providing accurate band gaps, the present database will be useful in screening materials in diverse applications.

scholarly journals Chern and Z2 topological insulating phases in perovskite-derived 4d and 5d oxide buckled honeycomb lattices

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Okan Köksal ◽  
Rossitza Pentcheva
Keyword(s):  
Lattice Constant ◽  
Density Functional ◽  
Strong Dependence ◽  
Density Functional Theory Calculations ◽  
Coulomb Repulsion ◽  
Band Gaps ◽  
Edge States ◽  
Topological Properties ◽  
Gap Opening ◽  
A Site

AbstractBased on density functional theory calculations including a Coulomb repulsion parameter U, we explore the topological properties of (LaXO3)2/(LaAlO3)4 (111) with X = 4d and 5d cations. The metastable ferromagnetic phases of LaTcO3 and LaPtO3 with preserved P321 symmetry emerge as Chern insulators (CI) with C = 2 and 1 and band gaps of 41 and 38 meV at the lateral lattice constant of LaAlO3, respectively. Berry curvatures, spin textures as well as edge states provide additional insight into the nature of the CI states. While for X = Tc the CI phase is further stabilized under tensile strain, for X = Pd and Pt a site disproportionation takes place when increasing the lateral lattice constant from aLAO to aLNO. The CI phase of X = Pt shows a strong dependence on the Hubbard U parameter with sign reversal for higher values associated with the change of band gap opening mechanism. Parallels to the previously studied (X2O3)1/(Al2O3)5 (0001) honeycomb corundum layers are discussed. Additionally, non-magnetic systems with X = Mo and W are identified as potential candidates for Z2 topological insulators at aLAO with band gaps of 26 and 60 meV, respectively. The computed edge states and Z2 invariants underpin the non-trivial topological properties.

The energy band structure of Si and Ge nanolayers

2016 ◽  
Vol 30 (34) ◽  
pp. 1650402 ◽  
Author(s):  
Xueke Wu ◽  
Weiqi Huang ◽  
Zhongmei Huang ◽  
Chaojie Qin ◽  
Yanlin Tang
Keyword(s):  
Band Gap ◽  
Energy Band ◽  
Density Functional ◽  
Band Gaps ◽  
First Principles Calculation ◽  
Generalized Gradient ◽  
Quantum Confinement Effects ◽  
Calculation Results ◽  
Direct Band ◽  
Band Gap Structure

First-principles calculation based on density functional theory (DFT) with the generalized gradient approximation (GGA) were carried out to investigate the energy band gap structure of Si and Ge nanofilms. Calculation results show that the band gaps of Si(111) and Ge(110) nanofilms are indirect structures and independent of film thickness, the band gaps of Si(110) and Ge(100) nanofilms could be transfered into the direct structure for nanofilm thickness of less than a certain value, and the band gaps of Si(100) and Ge(111) nanofilms are the direct structures in the present model thickness range (about 7 nm). Moreover, the changes of the band gaps on the Si and Ge nanofilms follow the quantum confinement effects. It will be a good way to obtain direct band gap emission in Si and Ge materials, and to develop Si and Ge laser on Si chip.

scholarly journals Oxygen decorating at the one ring and at the N-mouth of (10, 0) aluminum nitride nanotube: A DFT investigation

2014 ◽  
Vol 12 (2) ◽  
pp. 131-139
Author(s):  
Ahmad Seif ◽  
Lila Torkashavand ◽  
Fatemeh Mohammadi
Keyword(s):  
Density Functional Theory ◽  
Dipole Moment ◽  
Aluminum Nitride ◽  
Band Gap ◽  
Density Functional ◽  
Band Gaps ◽  
Chemical Shielding ◽  
Functional Theory ◽  
Aluminum Nitride Nanotube ◽  
The One

AbstractWe have investigated oxygen decorating in the (10, 0) aluminum nitride nanotube (AlNNT) by density functional theory. Band gaps, total (TDOS) and partial (PDOS) densities of state and chemical-shielding isotropic (CSI) and chemical-shielding anisotropic (CSA) have been calculated or determined in three models of the investigated (10, 0) AlNNT: pristine (model.0), O-decorating at the one ring in the middle of AlNNT (Model.1) and O-decorating at the nitrogen mouth of AlNNT (Model.2). The results indicated that the dipole moment does not detect the significant effects of dopant whereas TDOS, PDOS and band gap energies detect notable effects. The CSI and CSA values for the Al and N atoms-contributed to the Al-O bonds or those atoms close to the decorated region, in both models of O-decorated AlNNTs are changed.

scholarly journals Density Functional Theory (DFT) Study on α,α-Bis(2-benzothiophen-1-yl)-4H-cyclopenta[2,1-b,3;4-b′]dithiophene Derivatives for Optoelectronic Devices

2019 ◽  
Vol 8 (2) ◽  
pp. 126-139
Author(s):  
Banjo Semire ◽  
◽  
Olusegun Ayobami Odunola
Keyword(s):  
Density Functional Theory ◽  
Band Gap ◽  
Energy Band ◽  
Density Functional ◽  
Molecular Structures ◽  
Band Gaps ◽  
Photovoltaic Devices ◽  
Energy Band Gap ◽  
Functional Theory ◽  
Molecular Hyperpolarizability

Bis(2-benzothiophen-1-yl)-4H-cyclopenta[2,1-b,3;4-b′]dithiophene derivatives comprised of three series; bis(2-thienyl)-4H-cyclopenta[2,1-b,3;4-b]dithiopene (BTDT), diphenyl4Hcyclopenta[2,1-b,3;4-b]dithiophene (DPDT) and bis(2-benzothiophen-1-yl)-4Hcyclopenta[2,1-b,3;4-b]dithiophene (BBDT) have been studied using Density Functional Theory (B3LYP/6-31G**). In each series, molecules with C=S bridge exhibited the lowest band gap; for instance in BBDT series, the energy band gap could be arranged as 2.29, 2.23 and 1.66 eV for CH2, C=O and C=S bridge respectively. The low band gaps calculated for BBDT-C=S (1.66 eV) and BTDT-C=S (1.82 eV) could facilitate photo-excited electron transfer as one the criteria for a molecule to be used in photovoltaic devices. Also, the results showed that longest UV-vis absorption wavelength was observed for molecules with C=S bridge, i.e. 1013.66, 874.75 and 1097.66 nm for BTDT, DPDT and BBDT respectively. The polarizability (α0) valves calculated for the molecules follow as -CH2 < C=O < C=S bridge in each series, indicating that the higher the polarizability (α0) valve the longer the λmax nm and the lower the energy band gap. The magnitude of the molecular hyperpolarizability β0 showed that molecular structures with -C=O bridge could be best NLO material in each series.

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