Modeling of In0.17Ga0.83N/InxGa1–xN/AlyGa1–yN light emitting diode structure on ScAlMgO4 (0001) substrate for high intensity red emission

An In0.17Ga0.83N light emitting diode (LED) structure on ScAlMgO4 (0001) substrate is modeled for high intensity red emission. The high indium composition (In > 15%) inside the c-plane polar quantum well (QW) for longer wavelength emission degrades the structural and optical properties of LEDs because of induced strain energy and quantum confinement Stark effect. To compensate these effects, it has been demonstrated by simulation that an AlyGa1–yN cap layer of 2 nm thick and Al composition of 17% deposited onto QW of 3 nm thick and In composition of 35% will allow to have less defect density and higher intensity red emission at 663 nm than that of In0.17Ga0.83N/InxGa1–xN LEDs grown on ScAlMgO4 (0001) substrate. This LED structure has perfect in-plane equilibrium lattice parameter (αeq = 3.249 Å) and higher logarithmic oscillator strength (Γ = –0.93) values.

Structural, Electronic and Magnetic Properties of XYZ Type Half-Heusler Alloys

The spintronic devices have played an important role in modern technological era. Heusler alloys have attracted lot of interest in spintronic applications due to their half-metallic properties predicted by band structure calculations. We investigate the electronic, magnetic and structural properties of half-Heusleralloys FeMnGe and CoMnSb using first principles based density functional theory (DFT) implemented on Tight Binding Linear Muffin-Tin Orbital within Atomic Sphere Approximation (TB-LMTO-ASA) code. The calculation reveal that CoMnSb and FeMnGe are half-metallic Ferro-magnet in nature of with magnetic moment 1.00 μB and 2.99 μB per formula unit at equilibrium lattice parameter respectively. The magnetic moment mainly originates from the strong spin polarization of d electrons of X atom and partial contribution of p electrons of Y atom. The half metallic gap of FeMnGe and CoMnSb is found to be 0.38 eV and 0.95 eV respectively. This shows that these alloys are very promising spintronic functional materials.

Site-Preference, Electronic, Magnetic, and Half-Metal Properties of Full-Heusler Sc2VGe and a Discussion on the Uniform Strain and Tetragonal Deformation Effects

A hypothetical full-Heusler alloy, Sc2VGe, was analyzed, and the comparison between the XA and L21 structures of this alloy was studied based on first-principles calculations. We found that the L21-type structure was more stable than the XA one. Further, the electronic structures of both types of structure were also investigated based on the calculated band structures. Results show that the physical nature of L21-type Sc2VGe is metallic; however, XA-type Sc2VGe is a half-metal (HM) with 100% spin polarization. When XA-type Sc2VGe is at its equilibrium lattice parameter, its total magnetic moment is 3 μ B , and its total magnetism is mainly attributed to the V atom. The effects of uniform strain and tetragonal lattice distortion on the electronic structures and half-metallic states of XA-type Sc2VGe were also studied. All the aforementioned results indicate that XA-type Sc2VGe would be an ideal candidate for spintronics studies, such as spin generation and injection.

The effect of Ru on Ti50Pd50 high temperature shape memory alloy: a first-principles study

ABSTRACTThe stability of the Ti50Pd50-xRux alloy was investigated using first-principles density functional theory within the plane-wave pseudopotential method. Firstly, the Ti50Pd50 gave equilibrium lattice parameter and lowest heats of formation in better agreement with experimental data to within 3%. The heat of formation decreases with an increase in Ru concentration, consistent with the trend of the density of states which is lowered at the Fermi level as Ru content is increased which suggests stability. It was also found that from the calculated elastic constants the structures showed positive shear modulus above 20 at. % Ru, condition of stability. Furthermore, the addition of Ru was found to strengthen the Ti50Pd50-xRux system at higher concentrations. The thermal coefficients of linear expansion for the Ti50Pd31.25Ru18. 75 are higher at low temperature, and that the TiPd-Ru system tends to expand more at low content of 18.75 at. % Ru than at higher content. Partial substitution of Pd with Ru was found more effective as a strengthening element and may enhance the martensitic transformation temperature of the Ti50Pd50 alloy.

Исследование структуры и магнитных свойств сплавов Fe-=SUB=-8-=/SUB=-Rh-=SUB=-8-x-=/SUB=-Z-=SUB=-x-=/SUB=- (Z=Mn, Pt, Co; x=1, 2 и 3) первопринципными методами

The results of first-principles studies of the structure and magnetic properties of Fe–Rh–Z alloys conducted using the VASP package are reported. The magnetic moments and lattice parameters are determined, and the possibility of existence of stable tetragonal distortions in Fe–Rh–Z alloys with various magnetic configurations set by the level of doping with Mn, Pt, and Co is examined. It is demonstrated that the equilibrium lattice parameter and the type of magnetic ordering change with the concentration of the third element.

Структурные, магнитные, электронные и термодинамические свойства сплавов Гейслера Pd-=SUB=-2-=/SUB=-MnZ (Z=Ga, Ge, As): исследование ab initio

The results of examination of the structural, magnetic, electronic, and thermodynamic properties of Pd_2MnZ (Z = Ga, Ge, As) Heusler alloys obtained in ab initio and Monte Carlo modeling are presented. It is demonstrated that a stable martensitic state is possible for Pd_2MnGa and Pd_2MnAs alloys. The equilibrium lattice parameter increases in the considered series of alloys with the number of valence electrons per atom ( e / a ). The Curie temperature of Pd_2MnZ (Z = Ga, Ge, As) alloys is determined using the calculated parameters of exchange interaction and total magnetic moments.

Structural, Mechanical and Thermodynamic Properties under Pressure Effect of Rubidium Telluride: First Principle Calculations

First-principles density functional theory calculations have been performed to investigate the structural, elastic and thermodynamic properties of rubidium telluride in cubic anti-fluorite (anti-CaF2-type) structure. The calculated ground-state properties of Rb2Te compound such as equilibrium lattice parameter and bulk moduli are investigated by generalized gradient approximation (GGA-PBE) that are based on the optimization of total energy. The elastic constants, Young’s and shear modulus, Poisson ratio, have also been calculated. Our results are in reasonable agreement with the available theoretical and experimental data. The pressure dependence of elastic constant and thermodynamic quantities under high pressure are also calculated and discussed.

The First Principle Studies on the Ferromagnetic Shape Memory Effect of Ni2YIn(Y=Fe, Co) Heusler Alloys

The atom occupied sites, structures, tetragonal transformation and magnetic properties are studied by the first principles calculations. From least energy principle, the calculated equilibrium lattice parameter is 6.03 Å and 6.00 Å for Cu2MnAl type Ni2YIn (Y=Fe, Co) alloys, respectively. The Ni2YIn (Y=Fe, Co) alloys show steady martensitic phases at c/a=1.29 and c/a=1.36 based on the EBP’s method. Ni atoms and Y (Y=Fe, Co) contribute to the total magnetic moments, and keep parallel aligned in martensitic and austenitic phases. The Ni2YIn (Y=Fe, Co) alloys are the candidates for Ferromagnetic Shape Memory Alloys.

Molecular Dynamics Simulation of Pd and PdH Structure

For materials, science it is important to study the structure and behavior of matter at the deepest level. Currently, modern microscopes allow one to see the atomic structure of matter. Materials should be prepared in a special way, for research in the microscope, but thus the natural structure of the material may changed. Especially, the processes at the atomic level are difficult to explore. In a computer model of matter, one can account the properties of atoms and even its electron structure. In this paper, by molecular dynamics method the structure and evolution of the palladium and its compounds with hydrogen are investigated. In the work equilibrium structure of the crystal lattice of palladium was obtained and determined the equilibrium lattice parameter at different temperatures. The behavior of the hydrogen atom inside the crystal lattice of palladium was studied. The structural and diffusion properties system palladium-hydrogen were obtained

Takagi–Sugeno Fuzzy System to Predict Discharge Ignition Probability in the Foreline Pressure Range

For materials, science it is important to study the structure and behavior of matter at the deepest level. Currently, modern microscopes allow one to see the atomic structure of matter. Materials should be prepared in a special way, for research in the microscope, but thus the natural structure of the material may changed. Especially, the processes at the atomic level are difficult to explore. In a computer model of matter, one can account the properties of atoms and even its electron structure. In this paper, by molecular dynamics method the structure and evolution of the palladium and its compounds with hydrogen are investigated. In the work equilibrium structure of the crystal lattice of palladium was obtained and determined the equilibrium lattice parameter at different temperatures. The behavior of the hydrogen atom inside the crystal lattice of palladium was studied. The structural and diffusion properties system palladium-hydrogen were obtained