scholarly journals Crystal structure of rare earth and group III nitride alloys by ab initio calculations

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Maciej J. Winiarski ◽  
Dorota A. Kowalska
Keyword(s):  
Rare Earth ◽  
Density Functional ◽  
Metastable Phase ◽  
Rare Earth Ions ◽  
Ternary Alloys ◽  
Wurtzite Phase ◽  
Functional Theory ◽  
Group Iii ◽  
The Density Functional Theory ◽  
Group Iii Nitride

Abstract The ground state phases of ternary alloys of rare earth and group III nitride semiconductors have been investigated within the density functional theory. The most energetically favorable crystal phases among possible cubic and hexagonal structures, i.e., the rock salt, zinc blende, wurtzite, and hexagonal BN, were determined. The type of a unit cell and the lattice parameters of the materials are presented as a function of their composition. Furthermore, effects of strain on ground states of group III and rare earth nitride materials are discussed. The findings presented in this work discloses the wurtzite type materials as being stable with relatively low contents of rare earth elements. It is expected that the wurtzite phase will be very persistent only in the La-based systems. Nevertheless, the two-dimensional hexagonal atomic layers are revealed as being a metastable phase for all alloys studied. This finding supports the conclusion of previous experimental reports for Sc-doped GaN systems that the presence of rare earth ions in group III nitride materials leads to flattening of the wurtzite type layers.

Stoichiometry and Structure of Polar Group-III Nitride Semiconductor Surfaces

1997 ◽  
Vol 492 ◽  
Author(s):  
J. Fritsch ◽  
O. F. Sankey ◽  
K. E. Schmidt ◽  
J. B. Page
Keyword(s):  
Density Functional ◽  
Co Adsorption ◽  
Growth Conditions ◽  
Polar Group ◽  
Wurtzite Phase ◽  
Functional Theory ◽  
Group Iii ◽  
Metal Atoms ◽  
Total Energies ◽  
Group Iii Nitride

ABSTRACTWe use a local-orbital formalism based on density-functional theory to investigate the stoichiometry and structure of the cation- and anion-terminated (0001) surfaces of wurtzite-phase GaN and A1N. We compare the total energies computed for various p(2×2) reconstructions. First-layer atom deficient structures such as vacancies are found to be the most stable configurations for the anion- and cation-terminated surfaces. For metal rich growth conditions our calculations favor the adsorption of metal atoms. Surface chemical reactions relevant for the growth of thin nitride films, such as the adsorption of hydrogen and nitrogen from decomposed ammonia, are discussed. We determine the total energy differences for the co-adsorption of NH2 and H on different surface structures.

Metal-Oxygen Hybridization and Core-Level Spectra in Actinide and Rare-Earth Oxides

MRS Advances ◽  
2016 ◽  
Vol 1 (44) ◽  
pp. 3007-3012 ◽  
Author(s):  
Jindřich Kolorenč
Keyword(s):  
Rare Earth ◽  
Density Functional ◽  
Mean Field Theory ◽  
Mean Field ◽  
Core Level ◽  
Dynamical Mean Field Theory ◽  
Functional Theory ◽  
The Core ◽  
The Density Functional Theory ◽  
Rare Earth Sesquioxides

ABSTRACT We employ a combination of the density-functional theory and the dynamical mean-field theory to study the electronic structure of selected rare-earth sesquioxides and dioxides. We concentrate on the core-level photoemission spectra, in particular, we illustrate how these spectra reflect the integer or fractional filling of the 4f orbitals. We compare the results to our earlier calculations of actinide dioxides and analyze why the core-level spectra of actinide compounds display a substantially reduced sensitivity to the filling of the 5f orbitals.

scholarly journals Mechanical Response of PbSSe, PbSTe Ternary and PbSnSTe Quaternary Alloys at High Pressure

2020 ◽  
Vol 8 (2) ◽  
pp. 29-33
Author(s):  
Mazin Sh. Othman
Keyword(s):  
High Pressure ◽  
Density Functional ◽  
Mechanical Response ◽  
Ternary Alloys ◽  
Published Data ◽  
Quaternary Alloys ◽  
Linear Elasticity Theory ◽  
Functional Theory ◽  
Lattice Matching ◽  
The Density Functional Theory

Property of the semiconductors under high pressure is investigated by the density functional theory and paralleled to the foretelling of the linear elasticity theory. In addition, ternary alloys of  PbSxSe1-x and  PbSxTe1-x lattice matching PbS substrate for x = 0.5 compositions are studied. Furthermore, quaternary alloys PbxSn1-xSyTe1-y lattice matching PbS substrate for x  and y = 0.5 compositions are studied. The six independent elastic parameters (Cij) are also calculated. Meanwhile, the results data are analyzed in high pressure. The mechanical response of all alloys to pressures 0, 50, and 100 kbar increases progress to decrease in (Cij) in separate rates. The rapprochement between the calculated results and the available published data for these alloys demonstrate that they had worthy accordance at zero pressure and the results at high pressure may be required as an acceptable reference.

scholarly journals Spin-Filtering Effects in Würtzite and Graphite-Like AlN Nanowires with Mn Impurities

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
G. A. Nemnes
Keyword(s):  
Phase Transition ◽  
Density Functional ◽  
Surface States ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Group Iii ◽  
Magnetic Nanowire ◽  
Group Iii Nitride ◽  
Basic Prerequisite ◽  
Spin Filtering

Spin transport properties of magnetic nanowire systems—atomic-sized AlN nanowires with additional Mn impurities—are investigated employingab initioconstrained spin density functional theory calculations and nonequilibrium Green’s functions formalism. The analyzed nanowire structures exhibit a stress-induced phase transition, between würtzite and graphite-like configurations. In these quasi-one dimensional systems, the surface states ensure the basic prerequisite in establishing spin and charge transfer, by reducing the relatively large bandgap of the group III nitride semiconductor. The results show in how far this phase transition affects the surface states, focusing on the consequences which appear in the spin-filtering processes.

Mechanical Properties of Ti1-x-yAlxSiyN Nanocomposite Studied by Ab Initio

2012 ◽  
Vol 155-156 ◽  
pp. 926-930
Author(s):  
Xin Tan ◽  
Zhen Yang Xin ◽  
Xue Jie Liu ◽  
Yu Qing Li
Keyword(s):  
Mechanical Properties ◽  
Cohesive Energy ◽  
Density Functional ◽  
Mechanical Performance ◽  
Metastable Phase ◽  
Lattice Parameter ◽  
First Principles Calculations ◽  
Functional Theory ◽  
Al Content ◽  
The Density Functional Theory

Using first principles calculations based on the density functional theory, we have studied the structural and mechanical properties of Ti1-xAlxN and Ti1-x-yAlxSiyN metastable phase. Focus on the calculation of the Ti1-x-yAlxSiyN the cohesive energy, mechanical constants, elastic modulus and shear modulus. These calculated values were analyzed, then we obtained that Ti1-xAlxN lattice parameter decreased after adding Si, while the cohesive energy was rising, the mechanical properties decreased, indicating that in the case of the Al content determined, the structure of Ti1-x-yAlxSiyN is more stable than Ti1-xAlxN, but the mechanical performance ,stiffness and brittleness are reduced.

scholarly journals Магнитострикция в сплавах Fe-=SUB=-75-=/SUB=-Ga-=SUB=-25-x-=/SUB=-Z-=SUB=-x-=/SUB=- (Z=Al, Ge, Si): расчет методом магнитного вращающего момента

2021 ◽  
Vol 63 (11) ◽  
pp. 1745
Author(s):  
М.В. Матюнина ◽  
М.А. Загребин ◽  
В.В. Соколовский ◽  
В.Д. Бучельников
Keyword(s):  
Elastic Modulus ◽  
Density Functional ◽  
Ternary Alloys ◽  
Ab Initio Study ◽  
Magnetic Torque ◽  
Functional Theory ◽  
Cubic Crystal ◽  
Lattice Constants ◽  
Magnetoelastic Properties ◽  
The Density Functional Theory

This work presents an ab initio study of the effect of a small addition of the third element of III and IV groups on the elastic and magnetoelastic properties of Fe75Ga25 alloy. The dependencies of the tetragonal elastic modulus C', magnetoelastic constant –b1, and the tetragonal magnetostrictive constant λ001 on the concentration of the Z-element in the cubic crystal structures A2 and D03 were obtained with the help of the density functional theory and the magnetic torque method in Fe75Ga25-xZx (Z = Al, Ge, Si) alloys (0≤x≤6 at.%). It is shown that the addition of Al and Si atoms leads to an increase in the tetragonal elastic modulus compared to the Fe75Ga25 binary alloy. A correlation was established in the dependence equilibrium lattice constants a0(x) and λ001(x) in the studied ternary alloys for the A2 structure.

First-Principles Study of the Effect of Cr Content on Interstitial Oxygen Solution Behavior in Nb-Cr Alloys

2018 ◽  
Vol 913 ◽  
pp. 582-588
Author(s):  
Jin Wang ◽  
Li Ming Yu ◽  
Yong Chang Liu ◽  
Chen Xi Liu ◽  
Hui Jun Li ◽  
...  
Keyword(s):  
Density Functional ◽  
Ternary Alloys ◽  
Interstitial Oxygen ◽  
Solution Behavior ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Two Factors ◽  
Oxygen Solution ◽  
Cr Concentration ◽  
Interstitial Elements

The solution behavior of oxygen atom in Nb-Cr alloys was investigated by employing the density-functional theory. The solution behavior mainly depends on two factors, namely, the elastic and chemical interactions. We proposed a method to separate these two parts and applied it in Nb-Cr-O system to investigate the effect of alloying Cr concentration on the solution behavior of interstitial oxygen atoms. This method can be useful for understanding and predicting the solution behavior in ternary alloys which contain interstitial elements.

Remarkable Rashba spin splitting induced by an asymmetrical internal electric field in polar III–VI chalcogenides

2020 ◽  
Vol 22 (16) ◽  
pp. 9148-9156 ◽  
Author(s):  
Weiwei Ju ◽  
Donghui Wang ◽  
Tongwei Li ◽  
Yi Zhang ◽  
Zijian Gao ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Spin Splitting ◽  
Polar Group ◽  
Internal Electric Field ◽  
Functional Theory ◽  
Group Iii ◽  
Rashba Spin ◽  
The Density Functional Theory ◽  
Rashba Spin Splitting

The Rashba spin splitting of polar group III–VI chalcogenides XABY (A, B = Ga, In; X ≠ Y = S, Se, Te) monolayer is investigated based on the density functional theory.

Structure Study of ZnO:Eu with the Supercell Method

2010 ◽  
Vol 9 ◽  
pp. 25-30 ◽  
Author(s):  
A. Blanca-Romero ◽  
A. Flores-Riveros ◽  
J.F. Rivas-Silva
Keyword(s):  
Density Functional Theory ◽  
Rare Earth ◽  
Solid State ◽  
Density Functional ◽  
Cell Model ◽  
Structure Study ◽  
Functional Theory ◽  
Kondo Resonance ◽  
Super Cell ◽  
The Density Functional Theory

One of the interests on the study of doped materials with rare earths in their bulk or nanoscale size is owing to the enhancement of the intensity of light in their photoluminescence when a lanthanide exists in a receptor material, as ZnO in our case. Until now, one of the most useful theories for calculations of electronic properties in molecular and solid state systems is the Density Functional Theory (DFT), which is not capable to manage well the presence of high localized electrons, as in lanthanide compounds in general and the doped case in particular. We propose to study these materials with super cell model using some correction to the standard calculations. For this goal, we employ the WIEN2k [1] code using the LDA+U approximation to take into account the strong correlation of the f electrons coming from the lanthanide. We emphasise the study of deformation due to the presence of Eu ion in the structure of host material, optimizing the position of neighboring Oxygen atoms. This deformation has been related to Kondo Resonance [2] appearing around the Fermi Energy of the compound, due to hybridization [3] among the f electrons from rare earth and neighboring oxygen levels.

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