scholarly journals Y2O3:Eu and the Mössbauer isomer shift coefficient of Eu compounds from ab-initio simulations

2021 ◽  
Author(s):  
Arkadiy Davidov ◽  
Antonio Sanna ◽  
Giorgio Concas
Keyword(s):  
Charge Density ◽  
Isomer Shift ◽  
Density Functional ◽  
Mixed Valence ◽  
Accurate Estimation ◽  
Full Potential ◽  
Ab Initio Simulations ◽  
Mixed Valence Compounds ◽  
Contact Charge Density ◽  
The Eu

Abstract We report on a full potential density functional theory characterization of Y2O3 upon Eu doping on the two inequivalent crystallographic sites 24d and 8b. We analyze local structural relaxation,electronic properties and the relative stability of the two sites. The simulations are used to extract the contact charge density at the Eu nucleus. Then we construct the experimental isomer shift versus contact charge density calibration curve, by considering an ample set of Eu compounds : EuF3, EuO,EuF2, EuS, EuSe, EuTe, EuPd3 and the Eu metal. The, expected, linear dependence has a slope of α= 0.054 mm/s/Å3, which corresponds to nuclear expansion parameter ∆R/R= 6.0·10−5.αallows to obtain an unbiased and accurate estimation of the isomer shift for any Eu compound. We test this approach on two mixed-valence compounds Eu3S4 and Eu2SiN3, and use it to predict theY2O3:Eu isomer shift with the result +1.04 mm/s at the 24d site and +1.00 mm/s at the 8b site.

scholarly journals Thermoelectric properties of CeNi2Al3 compound: an experimental and theoretical study

2019 ◽  
Vol 125 (11) ◽  
Author(s):  
A. Szajek ◽  
A. Kowalczyk
Keyword(s):  
Thermoelectric Properties ◽  
Wide Temperature Range ◽  
Density Functional ◽  
Mixed Valence ◽  
Site Preference ◽  
Full Potential ◽  
Temperature Range ◽  
Broad Maximum ◽  
The Density Functional Theory ◽  
Mixed Valence Compounds

Abstract We present thermoelectric properties of the CeNi2Al3 compound in the temperature range from 4 to 300 K. The electrical resistance (ρ) exhibits a metallic-like character reaching approximately 50 μΩ cm at room temperature. The temperature dependence of the Seebeck coefficient (S) is typical for mixed valence compounds having positive values with a broad maximum (~ 46 μV/K) over a wide temperature range from 200 to 300 K. The thermal conductivity (κ) value reaches 15 W/(m K) at T = 300 K. The power factor (PF = S2/ρ) at 150 K is high (~ 70 μW/cm K2), larger than for conventional thermoelectric materials based on Bi2Te3. The dimensionless figure of merit (ZT) has a broad maximum over a wide temperature range, which reaches the value of 0.1 around 220 K. The experimental results are supported by calculations within the density functional theory (DFT) performed on the basis of the full-potential local-orbital minimum-basis scheme (FPLO). The coherent potential approximation (CPA) is used to simulate the chemical disorder. The calculations are focused on the site preference of Ni and Al atoms. Investigations of the energetic stability have shown that in CeNi2Al3 the aluminum atoms prefer the 3g sites and the nickel ones the 2c sites.

ELECTRONIC STRUCTURE AND ELECTRON CHARGE DENSITY IN THE INTERATOMIC BONDS OF BiSBr and BiSeBr CRYSTALS

2013 ◽  
Vol 27 (23) ◽  
pp. 1350122 ◽  
Author(s):  
A. AUDZIJONIS ◽  
R. SEREIKA
Keyword(s):  
Electronic Structure ◽  
Charge Density ◽  
Density Functional ◽  
Partial Density ◽  
Electronic Charge ◽  
Full Potential ◽  
Electron Charge ◽  
Generalized Gradient ◽  
Electron Charge Density ◽  
Plane Wave Method

Electronic structure and electronic charge density in the interatomic bonds are investigated with ab initio calculations based on the density-functional theory. The full potential linearized augmented plane-wave method was used with the generalized gradient approximation. Considering the partial density of states the electron charge density distribution in the Bi , S , Se and Br atomic bonds is caused by Bi-6p , S-3p , Se-4p , Br-4p orbital hybridization. Electronic charge distribution of one BiSBr and BiSeBr molecule range suggest that the Bi – S , Bi – Se and Bi – Br bonds are covalent–ionic type. Bi – S and Bi – Se bonds are strong covalent with a not great ionicity factor ([Formula: see text], Bi – S ; [Formula: see text], Bi – Se ). Bi – Br bonds are covalent type with a larger ionicity factor ([Formula: see text], Bi – Br ).

PHONONS IN MIXED VALENCE COMPOUNDS

1981 ◽  
Vol 42 (C6) ◽  
pp. C6-3-C6-10 ◽  
Author(s):  
W. Kress ◽  
H. Bilz ◽  
G. Güntherodt ◽  
A. Jayaraman
Keyword(s):  
Mixed Valence ◽  
Mixed Valence Compounds

First principles calculation of structural, electronic and optical properties of (001) and (110) growth axis (InN)/(GaN)n superlattices

2021 ◽  
Vol 67 (1 Jan-Feb) ◽  
pp. 7
Author(s):  
B. Bachir Bouiadjra ◽  
N. Mehnane ◽  
N. Oukli
Keyword(s):  
Optical Properties ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Scale Up ◽  
Energy Scale ◽  
First Principles Calculation ◽  
Full Potential ◽  
Electronic Band ◽  
Electronic And Optical Properties ◽  
Growth Axis

Based on the full potential linear muffin-tin orbitals (FPLMTO) calculation within density functional theory, we systematically investigate the electronic and optical properties of (100) and (110)-oriented (InN)/(GaN)n zinc-blende superlattice with one InN monolayer and with different numbers of GaN monolayers. Specifically, the electronic band structure calculations and their related features, like the absorption coefficient and refractive index of these systems are computed over a wide photon energy scale up to 20 eV. The effect of periodicity layer numbers n on the band gaps and the optical activity of (InN)/(GaN)n SLs in the both  growth axis (001) and (110) are examined and compared. Because of prospective optical aspects of (InN)/(GaN)n such as light-emitting applications, this theoretical study can help the experimental measurements.

scholarly journals Mixed-valence Compounds: AuO2 and AuS

ChemPhysChem ◽  
2018 ◽  
Vol 19 (22) ◽  
pp. 2971-2971
Author(s):  
Meng Tang ◽  
Yanmei Zhang ◽  
Siya Li ◽  
Xi Wu ◽  
Yan Jia ◽  
...  
Keyword(s):  
Mixed Valence ◽  
Mixed Valence Compounds

scholarly journals The effect of pressure and alloying on half-metallicity of quaternary Heusler compounds CoMnYZ (Z = Al, Ga, and In)

2016 ◽  
Vol 34 (4) ◽  
pp. 905-915 ◽  
Author(s):  
M. Rahmoune ◽  
A. Chahed ◽  
A. Amar ◽  
H. Rozale ◽  
A. Lakdja ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Density Functional ◽  
Heusler Alloys ◽  
Band Gaps ◽  
Ferromagnetic Behavior ◽  
Full Potential ◽  
Energy Bands ◽  
Half Metallicity ◽  
Half Metallic ◽  
Electronic And Magnetic Properties

AbstractIn this work, first-principles calculations of the structural, electronic and magnetic properties of Heusler alloys CoMnYAl, CoMnYGa and CoMnYIn are presented. The full potential linearized augmented plane waves (FP-LAPW) method based on the density functional theory (DFT) has been applied. The structural results showed that CoMnYZ (Z = Al, Ga, In) compounds in the stable structure of type 1+FM were true half-metallic (HM) ferromagnets. The minority (half-metallic) band gaps were found to be 0.51 (0.158), 0.59 (0.294), and 0.54 (0.195) eV for Z = Al, Ga, and In, respectively. The characteristics of energy bands and origin of minority band gaps were also studied. In addition, the effect of volumetric and tetragonal strain on HM character was studied. We also investigated the structural, electronic and magnetic properties of the doped Heusler alloys CoMnYGa1−xAlx, CoMnYAl1−xInx and CoMnYGa1−xInx (x = 0, 0.25, 0.5, 0.75, 1). The composition dependence of the lattice parameters obeys Vegard’s law. All alloy compositions exhibit HM ferromagnetic behavior with a high Curie temperature (TC).

First principles calculations of structural, electronic and optical properties of InN compound

2015 ◽  
Vol 29 (05) ◽  
pp. 1550028 ◽  
Author(s):  
R. Graine ◽  
R. Chemam ◽  
F. Z. Gasmi ◽  
R. Nouri ◽  
H. Meradji ◽  
...  
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Density Functional ◽  
Local Density ◽  
Indium Nitride ◽  
Alternative Form ◽  
Full Potential ◽  
Generalized Gradient ◽  
Pressure Derivative ◽  
Electronic And Optical Properties

We carried out ab initio calculations of structural, electronic and optical properties of Indium nitride ( InN ) compound in both zinc blende and wurtzite phases, using the full-potential linearized augmented plane wave method (FP-LAPW), within the framework of density functional theory (DFT). For the exchange and correlation potential, local density approximation (LDA) and generalized gradient approximation (GGA) were used. Moreover, the alternative form of GGA proposed by Engel and Vosko (EV-GGA) and modified Becke–Johnson schemes (mBJ) were also applied for band structure calculations. Ground state properties such as lattice parameter, bulk modulus and its pressure derivative are calculated. Results obtained for band structure of these compounds have been compared with experimental results as well as other first principle computations. Our results show good agreement with the available data. The calculated band structure shows a direct band gap Γ → Γ. In the optical properties section, several optical quantities are investigated; in particular we have deduced the interband transitions from the imaginary part of the dielectric function.

Sign in / Sign up

Export Citation Format

Share Document