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Density functional theory with pesudo potential approximation is used to study XBaB (X = Li , Na, K) half-Heusler compounds structural, magnetic and electrical property using Quantum espresso code and thermoelectric properties were studied using BoltzTrap code. Total energy calculations were carried out in the α , β and γ phases of XBaB compounds in C 1 b type structure. The compounds were stable in α -phase and hence further calculations were focused only on α phase. From the spin polarization calculations, magnetic state was stable than nonmagnetic state and exhibits ferromagnetism at the equilibrium lattice constant with an integer magnetic moment of 2  μ B . From the band structure calculations and through density of states, all the three compounds exhibit half-metallicity with 100% spin polarization by showing semi-conductivity for majority spin and metallicity for minority spin. In addition, thermoelectric properties were investigated for all three compounds. LiBaB is found to have high Seebeck coefficient of 2462 μ VK − 1 and ZT value of 1, compared to other compounds. These materials were found to have high ZT value and hence they can be used for thermoelectric applications. [ABSTRACT FROM AUTHOR]

The Goos–Hänchen (GH) shift and the spin polarization are theoretically investigated under the anti-parallel double δ -magnetic-barrier nanostructure model by applying a bias using Airy's function formalism and transfer-matrix technique, which is an improvement on previous calculation. The results show the magnitude and sign of GH shift and spin polarization can be easily changed by modulating the applied bias. The closer the applied bias to the critical value is, the more intensive GH shift and spin polarization will be. Furthermore, two critical values come through modulating the strength of magnetic fields, and an intensive GH shift and a spin polarization also exist near each critical value. These findings can provide a practical approach to designing and fabricating spin beam filters or splitters modulated by applied bias. [ABSTRACT FROM AUTHOR]

The Rashba spin–orbit coupling (RSOC) effect on the polarization and shot noise properties in a strained WSe2 multiple barrier structure is studied by transfer-matrix technique. The results indicate that the spin-dependent Fano factor depends on the strain and RSOC strength with oscillatory evolution. Thus, the value of Fano factor with spin rotation can be tuned mechanically and by an external electric field. Also, Fano factor shows high sensitivity to the number of electrostatic barriers in strained WSe2 multiple barrier structure. Meanwhile, in a strained WSe2 multiple barrier structure both sign and value of the valley and spin polarizations could be adjusted by tuning both RSOC and strain strength. These findings show that a WSe2 multiple barrier structure under strain and RSOC can be useful for future spintronics, straintronic and valleytronic devices. [ABSTRACT FROM AUTHOR]

Based on the density functional theory (DFT) calculations, the structural, electronic, optical and thermoelectric properties of the MnFeTe Heuslerene compound have been investigated. The total energy change curve in terms of volume refers to the ground state point and equilibrium volume. By applying mBJ approximation, this compound has perfect half-metallic behavior of 100% spin polarization at the Fermi level with 7 μ B magnetic moment. Optical calculations show that the semiconductor behavior with an optical absorption gap occurred by incident light perpendicular to the MnFeTe Heuslerene plane. The figure of merit coefficient (ZT) has reached 3.5 at 50 K temperature, which makes it an excellent candidate for thermoelectric applications. Also, the power factor (PF) of this compound has reached its maximum value at room temperature. [ABSTRACT FROM AUTHOR]

In this work, the effects of magnetic proximity coupling on electronic structures, valley polarization and magneto-crystal anisotropy of VI3/WSe2 heterostructure are studied in detail based on density functional theory. The results show that the spin-valley polarization characters of WSe2 monolayer can be induced by the proximity effect of ferromagnetic VI3 monolayer. Based on the effective Hamiltonian k ⋅ p model, a large valley polarization of 8.7 meV is observed, which is mainly contributed by the SOC effect and not magnetic exchange field. Meanwhile, the magneto-crystal anisotropy of VI3 layer is also obviously altered from the [100] to [001] magnetic axis compared to the isolated VI3 monolayer. The reduction in the interlayer space strengths the W–V atomic coupling, resulting in a significant increase in the spin and valley polarization. Compression strain shows weakening effect on the valley polarization, while the tensile strain largely enhances the valley polarization of VI3/WSe2 heterostructure, which can reach the maximum value of 29.1 meV at the tensile strain of 8%. The V spin direction (θ) has significant effect on valley polarization of WSe2 layer, which is positively correlated with the magnetization strength of V atom in the vertical direction. Furthermore, constructing the VI3/WSe2/VI3 sandwich heterostructure can induce a larger valley polarization, which can reach a maximum value of 32.4 meV. These results indicate that the VI3/WSe2 heterostructure is a potential candidate for valleytronics. [ABSTRACT FROM AUTHOR]

By employing the first principles method within the generalized gradient approximation for the exchange and correlation potential, the electronic, optical and magnetic properties of pure and Fe-doped zinc-blende ZnSe are investigated. According to the obtained band structure, density of state and optical spectrum the electronic origin of the maxima in the optical spectrum has been observed. The optical spectrum peak is generated mainly from the charge transfer between the Se(4 p) and Zn(3 p) states. Our results reveal that the strong spin polarization of the 3 d states of the Fe atoms is the origin of antiferromagnetism in Zn 1 − x Fe x Se. A decrease in the concentration of iron atoms in the supercell does not affect the stability of the AFM phase. [ABSTRACT FROM AUTHOR]

This paper reports density functional theory (DFT) on LiMgP half Heusler alloy doped by the transition metal elements (Ti, V, Fe and Ni) determined by present results, in which the half-metallicity besides ferromagnetism behavior is estimated. The electron spin polarization of Ti(3 d) is around the E F and the Ti 2 + will have two electrons, of which two electrons occupied the e + . Then, this orbital is set on the Fermi level. When the conduction band of the orbitals e − , t 2 + and t 2 − is empty, LiMg 0. 9 5 Ti 0. 0 5 P displays the half-metallic characteristic, where the ferromagnetic (FM) conduct fits the double-exchange coupling. For LiMg 0. 9 5 V 0. 0 5 P alloy, the charge state is closer to V 2 + electron configuration, which predicts the following configuration, in which two electrons are occupied by e + and one electron is occupied by t 2 + at the upside of E F . Based on LiMg 0. 9 5 Fe 0. 0 5 P alloy, the presence of the half metallicity at the downside of E F due to (3 d) orbital is clear. A hybridization between the Fe(3 d) and the P(3 p) orbitals is in the range −0.35 — −0.04 Ry. For LiMg 0. 9 5 Ni 0. 0 5 P alloy, the predicted charge is Ni 2 + and exhibits the half-metallic on the downside of the E F which is occupied by t 2 − minority state. For LiMg 0. 9 5 TM 0. 0 5 P alloy, (TM = Ti, V, Fe and Ni), the half-metallic conduct is estimated with 100% spin polarized on the Fermi level. The spin moment of TM is ∥ M Ni ∥ < ∥ M Ti ∥ < ∥ M V ∥ < ∥ M Fe ∥ , where their total magnetic moments ∥ M Tot ∥ are in correlation for those Ni, Ti, V and Fe, where the trend also is ∥ M LiMg+ 0. 9 5 Ni 0. 0 5 P Tot ∥ < ∥ M LiMg 0. 9 5 Ti 0. 0 5 P Tot ∥ < ∥ M LiMg 0. 9 5 V 0. 0 5 P Tot ∥ < ∥ M LiMg 0.95 Fe 0. 0 5 P Tot ∥. Likewise, based on LiMg 0. 9 5 TM 0. 0 5 P alloys, the crystal field splitting (e , t 2) observation stated that the doped elements conduct a trend having the following range Δ (e , t 2) Ni < Δ (e , t 2) Ti < Δ (e , t 2) V < Δ (e , t 2) Fe . From these observations, it is predicted to have a correlation between magnetic moments of (Ti, V, Fe and Ni) and the crystal field splitting. [ABSTRACT FROM AUTHOR]

In this paper, we report the optoelectronic, thermoelectric properties and dynamic stability under the pressure of LiGaC half-Heusler within the Density Functional Theory (DFT) and semi-classical Boltzmann Transport Theory (BTT). The obtained results of the ground state show that the compound is structural, chemical, mechanical and dynamically stable in type I structure and maintains its stability under pressure. The obtained electronic properties reveal that the compound has a semiconducting nature with an indirect bandgap and the bandgap values slightly increase with pressure increase. The optical properties such as real and imaginary parts of dielectric function, refractive index and extinction coefficient, reflectivity and absorption coefficient and optical conductivity are calculated and discussed. The highest peaks of reflectivity and absorption coefficient are found in the ultra-violet (UV) region, suggesting that the compound LiGaC has a high potential for use in UV optoelectronic applications. The thermoelectric properties are also calculated in the temperature range from 300 K to 900 K and pressure range from 0 GPa to 40 GPa. At 300 K and for all pressures selected, the maximum value of figure of merit is close to unity. Finally, we could make our conclusion that LiGaC is well suitable for multiple optical and thermoelectric applications. [ABSTRACT FROM AUTHOR]

Based on density functional theory, structural, electronic, magneto-optic, and thermoelectric properties of RbCaN2 and RbCaO2, Heuslerene compounds have been calculated. These compounds have the ground state points with total magnetic moment of 1.0 μ B , which represents their ferromagnetic behavior. The RbCaN2 Heuslerene has the half-metallic nature and RbCaO2 case is a magnetic semiconductor. The Kerr angle of the RbCaN2 Heuslerene has two relatively peaks at the energies of 5.5 eV to 7.0 eV, but for the RbCaO2 compound, this diagram is wider in a larger energy range. Faraday angle peaks occurred at 6.2 eV and 6.8 eV for RbCaN2 and RbCaO2 compounds, which indicates the polarization of the light irradiated to them at these energies. It was observed that both compounds show high thermoelectric quality at temperatures higher than the room-temperature, and both compounds are suitable for power generator applications. [ABSTRACT FROM AUTHOR]

In this paper, site preference, phase stability and elastic parameters of MoSi2 for Al and Nb addition are studied using first-principles calculation. The results show that alloying elements can cause MoSi2 to change from C11b to C40 phase and the phase transition is due to the activated 1/2[ 1 ̄ 11](110) slip system for C11b. G ∕ B ratio reveals that the ductility is enhanced after phase transition. Ductile factor σ γ m ∕ σ c based on competitive processes between micro-crack opening and dislocations emission is defined to assess the ductility of MoSi2. Interestingly, the increased ductility is due to the activated dislocation emission but suppressed crack propagation. Finally, charge density and DOS indicate that the improved ductility is due to the weakened Mo-4d and Si-3p covalent interactions. [ABSTRACT FROM AUTHOR]

This work reports first-principle calculations for LiMgP half-Heusler compound doped by the transition metal elements Cr, Mn, Co and Ni motivated by present findings, in which the ferromagnetism conduct is predicted. The studied LiMg 0. 9 5 Y 0. 0 5 P alloy (Y = Cr , Mn, Co and Ni) showed the ferromagnetic behavior. The calculations revealed that the main contributions to the net magnetization come from Cr, Mn, Co and Ni. The Cr 2 + will have four electrons, in which 2 electrons are in e + and other 2 occupy the t 2 + . Then, this orbital is set on the Fermi level. For LiMg 0. 9 5 Co 0. 0 5 P alloy, the half-metallic conduct is estimated with 100% polarized on the downside of the Fermi level. Also, LiMg 0. 9 5 Ni 0. 0 5 P alloy exhibits the half-metallic conduct on the downside of the Fermi level which is occupied by t 2 − minority state. This study stated that electronegativity and magnetic properties have correlation with regard to Cr-, Mn-, Co- and Ni-doped LiMgP, in which the trends of partial moments, electronegativity and total moments are M Ni < M Co < M Cr < M Mn ; χ Ni > χ Co > χ Cr > χ Mn and M LiMg 0. 9 5 Ni 0. 0 5 P Tot < M LiMg 0. 9 5 Co 0. 0 5 P Tot < M LiMg 0. 9 5 Cr 0. 0 5 P Tot < M LiMg 0. 9 5 Mn 0. 0 5 P Tot . [ABSTRACT FROM AUTHOR]

In this research work, the two-dimensional (2D), incompressible fluid flow has been taken into consideration. The flow is supposed to be steady and laminar. By considering the water-based nanoparticles of SWCNTs and MWCNTs in the presence of thermal radiation, the rate of heat transferring and entropy generation effects in a regenerative cooling system of a rocket engine are evaluated. The effects of the length and radius of the nanomaterials on the problem are also considered. Solutions for temperature, velocity profile, irreversibility (entropy generation) and the Bejan number are discussed graphically, and the effects of various significant factors are considered on these profiles. The modeled physical problems in current exploration are dependent upon governing laws which appear in terms of PDEs. These PDEs are reformed into a system of nonlinear ODEs. We used numerical scheme known as (RK-4) in combination with the shooting iteration technique to obtain the solutions to transformed fluid flow equations, because the resultant ODEs are extremely nonlinear and finding the exact solution is very difficult. It is investigated that the Eckert number, nanoparticles volume fraction and radiation parameter upsurge the thermal field as well as the irreversibility of the system. Furthermore, the dual behavior of nanoparticles volume fraction and viscosity parameter on velocity profile is observed. Bejan number shows increasing effects in response to nanoparticles volume fraction and radiation parameter, whereas a reverse impact of Bejan number is noticed for the rising values of Eckert number. [ABSTRACT FROM AUTHOR]