Investigated electronic structure and magnetic ordering of rare earth impurities (Eu, Gd) in ZnO

2016 ◽  
Vol 30 (31) ◽  
pp. 1650225 ◽  
Author(s):  
F. Benosman ◽  
Z. Dridi ◽  
Y. Al-Douri ◽  
B. Bouhafs
Keyword(s):  
Electronic Structure ◽  
Rare Earth ◽  
Density Functional ◽  
Nearest Neighbor ◽  
Magnetic Coupling ◽  
Magnetic Ordering ◽  
Hole Doping ◽  
High Electron ◽  
Functional Theory ◽  
Good Agreement

First-principles calculations of the electronic structure of substitutional rare earth (RE) impurity (Eu and Gd) in wurtzite ZnO have been performed using density functional theory within a Hubbard potential correction to the RE 4f states. For Eu-doped ZnO, the magnetic coupling between Eu ions in the nearest neighbor sites is ferromagnetic (FM). The room temperature (RT) ferromagnetism (FM) can be enhanced by an appropriate hole doping into the sample. The ZnO:Gd is found to favor the antiferromagnetic (AFM) phase. The FM can be achieved by high electron doping. The native defects effect (V[Formula: see text], V[Formula: see text]) on the FM is also studied. The oxygen vacancies seem to play an important role in the generation of the FM in both ZnO:Eu and ZnO:Gd, which is in good agreement with recent experimental results.

Theoretical Study of the Electronic Structures of Li-Doped ZnO

2012 ◽  
Vol 535-537 ◽  
pp. 214-218
Author(s):  
Qi Xin Wan ◽  
Jia Yi Chen ◽  
Zhi Hua Xiong ◽  
Dong Mei Li ◽  
Bi Lin Shao ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Density Functional ◽  
Formation Energy ◽  
Lattice Distortion ◽  
Theoretical Study ◽  
Functional Theory ◽  
Li Doping ◽  
The Density Functional Theory ◽  
Doped Zno ◽  
Good Agreement

The first-principles with pseudopotentials method based on the density functional theory was applied to calculate the geometric structure, the formation energy of impurities and the electronic structure of Li-doped ZnO. In the system of Li-doped ZnO, LiZn can not result in lattice distortion. In contrast with that case, LiO and Lii result in lattice distortion after Li doping in ZnO. In Li-doped ZnO, LiO is the most unstable than the other cases. Simultaneously, Lii is more stable than LiZn according to that Lii has smaller formation energy. Furthermore, the electronic structure of Li-doped ZnO indicates that that LiZn behaves as acceptor, while Lii behaves as donor. In conclusion, in Li-doped ZnO, Lii is always in the system to compensate the acceptor. Singly doping Li in ZnO is difficult to gain p-ZnO for the self-compensation. The results are in good agreement with other calculated and experimental results.

Renormalization from Density Functional Theory to Strong Coupling Models for the Electronic Structure of La2CuO4

1989 ◽  
Vol 169 ◽  
Author(s):  
Mark S. Hybertsen ◽  
Michael Schluter ◽  
E.B. Stechel ◽  
D.R. Jennison
Keyword(s):  
Electronic Structure ◽  
Hubbard Model ◽  
Strong Coupling ◽  
Density Functional ◽  
Nearest Neighbor ◽  
Quantitative Agreement ◽  
Energy Scale ◽  
Low Energy ◽  
Energy Spectra ◽  
Functional Theory

AbstractStrong coupling models for the electronic structure of La2CuO4 are derived in two successive stages of renormalization. First, a three-band Hubbard model is derived using a constrained density functional approach. Second, exact diagonalization studies of finite clusters within the three band Hubbard model are used to select and map the low energy spectra onto effective one-band Hamiltonians. At each stage, some observables are calculated and found to be in quantitative agreement with experiment. The final results suggest the following models to be adequate descriptions of the low energy scale dynamics: (1) a spin 1/2 Heisenberg model for the insulating case with nearest neighbor J≈130 meV; (2) a "t–t'–J" model with nearly identical parameters for the electron and hole doped cases.

Effects of rare earth adsorption on electronic structure and optical properties in β-Si3N4 ceramics from first principles

RSC Advances ◽  
2014 ◽  
Vol 4 (96) ◽  
pp. 53570-53574 ◽  
Author(s):  
Yin Wei ◽  
Hongjie Wang ◽  
Xuefeng Lu ◽  
Jiangbo Wen ◽  
Min Niu ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Optical Properties ◽  
Electronic Structure ◽  
Rare Earth ◽  
Silicon Nitride ◽  
Rare Earths ◽  
First Principles ◽  
Density Functional ◽  
Functional Theory ◽  
Si3n4 Ceramics

Electronic structure and optical properties of silicon nitride adsorbed by rare earths are explored by density functional theory.

Electronic structure and spectroscopy of homoleptic compounds of dimolybdenum using TDDFT

2016 ◽  
Vol 94 (1) ◽  
pp. 20-27
Author(s):  
Pere Vilarrubias
Keyword(s):  
Experimental Data ◽  
Density Functional Theory ◽  
Electronic Structure ◽  
Density Functional ◽  
Molecular Orbitals ◽  
Time Dependent ◽  
Electronic Transitions ◽  
Functional Theory ◽  
Dependent Density ◽  
Good Agreement

Ten compounds of dimolybdenum are studied using density functional theory and time-dependent density functional theory. The energy of the strongest symmetry-allowed bands is calculated. The results are then compared with experimental data, when available. The PW91 functional gives results for geometry and for the energy of the δ→δ* band that show good agreement with experimental data. However, the B3LYP functional gives more realistic values for the whole spectrum when the results are compared with experimental data. Finally, the different values of energy of these bands are explained analyzing the molecular orbitals involved in these transitions. Some ligands can act as an unsaturated system in conjugation with the delta bond, modifying the energies of the electronic transitions.

Theoretical investigation of the magnetic ordering and the superconducting state in rare earth iron pnictides

2014 ◽  
Vol 03 (04) ◽  
pp. 1450020 ◽  
Author(s):  
S. Abbaoui ◽  
A. Zaoui ◽  
S. Kacimi ◽  
M. Djermouni ◽  
M. Bououdina
Keyword(s):  
Rare Earth ◽  
Density Functional ◽  
Local Density ◽  
Magnetic Ordering ◽  
Ferromagnetic State ◽  
Iron Pnictides ◽  
Density Approximation ◽  
Functional Theory ◽  
Fermi Surfaces ◽  
Hubbard U

The superconductivity and magnetic phenomena of the rare earth iron pnictides R FePO (R = La , Sm ) are analyzed using ab initio density functional theory in the local density approximation (LDA) with the on-site Hubbard U eff parameter (LDA + U). The results of the magnetic properties, band structures and Fermi surfaces of the recently synthesized tetragonal layered iron pnictides superconductor SmFePO are presented in comparison with the superconductor LaFePO . The anti-ferromagnetic state [ Sm : AFM, Fe AFM_stripe] is found to be the most stable than the other possible phases, which is in agreement with experiment. The effect of the Hubbard correction is investigated and is found to be a necessary requirement for the accurate description of both the electronic structure and the Fermi surfaces.

First-Principles Investigation of Electronic Structural and Optical Properties of Rare Earth Doped β-Si3N4 Crystals

2012 ◽  
Vol 512-515 ◽  
pp. 864-868 ◽  
Author(s):  
Dong Qiu ◽  
Xue Feng Lu ◽  
Bai Hai Li ◽  
Hong Jie Wang
Keyword(s):  
Rare Earth ◽  
Band Gap ◽  
Density Functional ◽  
Structural Parameters ◽  
Generalized Gradient ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Optical Dielectric Constant ◽  
Optical Dielectric ◽  
Good Agreement

Based on the density functional theory within the generalized gradient approximation (GGA) method, the geometric structure, electronic and dielectric properties of rare earth (La and Y) doped β-Si3N4 were studied and the origin of the differences and similarities among the rare earths (La and Y) characterized in this work were discussed. The fully relaxed structural parameters of β-SiN4 crystal are found to be in good agreement with experimental data. The formation energy calculations indicate that both La and Y atoms are preferentially doped on the Si sites, which is in agreement with previous experimental observations. Furthermore, the calculated band gap of the doped structures decreases significantly, specifically, the larger La atom results in narrower band gap than that of Y doped β-Si3N4. The reason was extensively analyzed by the density of states (DOS). Subsequently, the dielectric function, absorption coefficient of the polycrystalline were compared with these values for plane polarized at [100] and [001] directions. The calculations show that the optical dielectric constant in the rare earth (especially La) doped structures increase remarkably, compared with the undoped β-Si4N4.

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