Publication Date: 2024
Computational Condensed Matter (23522143)39
In this study, the structural, elastic, vibrational, electronic, optical, thermodynamic, and thermoelectric properties of the chalcogenide ternary Y2ZnX4 (Y = In, Ga; X = S, Se) compounds are comprehensively investigated using the pseudopotential plane-wave (PP-PW) and full-potential linearized augmented plane wave (FP-LAPW) methods. The analysis of elastic and vibrational properties reveals the dynamic and mechanical stability of these compounds. The calculated energy band gaps, ranging from 1.47 eV (Ga2ZnSe4) to 2.55 eV (In2ZnS4) in the visible spectrum, decrease as X atoms are substituted with S to Se. All examined compounds demonstrate favorable optical absorption (α > 105 cm−1) in the ultraviolet region. Notably, Ga2ZnSe4 exhibits absorption red-shift towards the visible region at hν = 2.76 eV due to its lower energy band gap, making it a promising candidate for solar cells. The three-dimensional representation of Young's modulus indicates significant deviation from sphericity, revealing anisotropic behavior in all compounds. Pugh's ratio, Poisson's ratio, and Cauchy's pressure analysis suggest ductile behavior in all four chalcogenide ternary compounds. Additionally, all compounds, except In2ZnS4, display auxetic properties. Finally, the calculated thermoelectric properties identify Ga2ZnS4 and In2ZnS4 as promising candidates for high-performance thermoelectric applications, with high Seebeck coefficients of 1848 and 1936 μV/K, respectively, and ZT values approaching unit. © 2024 Elsevier B.V.
Publication Date: 2022
Computer Physics Communications (0010-4655)271
We introduce a computational method and a user-friendly code with a terminal-based graphical user interface (GUI), named ElATools, developed to analyze mechanical and anisotropic elastic properties. ElATools enables facile analysis of the second-order elastic stiffness tensor of two-dimensional (2D) and three-dimensional (3D) crystal systems. It computes and displays the main mechanical properties including the bulk modulus, Young's modulus, shear modulus, hardness, p-wave modulus, universal anisotropy index, Chung-Buessem anisotropy index, log-Euclidean anisotropy parameter, Cauchy pressures, Poisson's ratio, and Pugh's ratio, using three averaging schemes of Voigt, Reuss, and Hill. It includes an online and offline database from the Materials Project with more than 13,000 elastic stiffness constants for 3D materials. The program supports output files of the well-known computational codes IRelast, IRelast2D, ElaStic, and AELAS. Four types of plotting and visualization tools are integrated to conveniently interface with GNUPLOT, XMGRACE, view3dscene and plotly libraries, offering immediate post-processing of the results. ElATools provides reliable means to investigate the mechanical stability based on the calculation of six (three) eigenvalues of the elastic tensor in 3D (2D) materials. It can efficiently identify anomalous mechanical properties, such as negative linear compressibility, negative Poisson's ratio, and highly-anisotropic elastic modulus in 2D and 3D materials, which are central properties to design and develop high-performance nanoscale electromechanical devices. Moreover, ElATools can predict the behavior of the sound velocities and their anisotropic properties, such as acoustic phase/group velocities and power flow angles in materials, by solving the Christoffel equation. Six case studies on selected material systems, namely, ZnAu2(CN)4, CrB2, δ-phosphorene, Pd2O6Se2 monolayer, and GaAs, and a hypothetical set of systems with cubic symmetry are presented to demonstrate the descriptive and predictive capabilities of ElATools. Program summary: Title: ElATools Licensing provisions: GNU General Public Licence 3.0 Nature of the problem: Identifying anisotropic elastic properties of 2D and 3D materials, and calculating acoustic phase and group velocities in homogeneous solids. Solution method: Second-order elastic stiffness tensor analysis using transformation law and calculations of the elastic surfaces properties. Solving the Christoffel equation eigenvalue problem using diagonalization and calculations of the sound velocities. Programming language: Fortran 90 Operating system: Unix/Linux/MacOS/Windows by Cygwin: http://www.cygwin.com/ Distribution format: tar.gz Required routines/libraries: LAPACK, BLAS, and Plotly Javascript libraries, GNUPLOT, XMGRACE, view3dscene. Computer: Any system with a Fortran 90 (F90) compiler Memory: Up to 1 GB for any symmetry Run time: Up to 70 seconds for any symmetry, and (400×400) = (θ×ϕ)-mesh in spherical coordinate Documentation: Available at https://yalameha.gitlab.io/elastictools/index.html © 2021 Elsevier B.V.
Publication Date: 2021
Materials Science and Engineering: B (09215107)273
We predict the highly stable new full-Heusler order compound Cs(Na, K)2Bi, that can take a diverse set of topological states by strain-engineering. Based on first-principles studies, our findings reveal that the hydrostatic lattice compression, uniaxial compression, and uniaxial tension can transition Cs(Na, K)2Bi to a trivial semiconductor, a normal insulator, a topological insulator, a Weyl semimetal, a Dirac semimetal, and a Nodal Line semimetal. These topological states, induced by various kinds of strain, exhibit a range of interesting optical and electronic transport properties. These results introduce Cs(Na, K)2Bi compounds as promising candidates to make novel topological devices whose properties can be controlled using strain-engineering. © 2021 Elsevier B.V.
Publication Date: 2021
Nanomaterials (20794991)11(10)
Using first‐principles calculations, we predict highly stable cubic bialkali bismuthides Cs(Na, K)2Bi with several technologically important mechanical and anisotropic elastic properties. We investigate the mechanical and anisotropic elastic properties under hydrostatic tension and compression. At zero pressure, CsK2Bi is characterized by elastic anisotropy with maximum and minimum stiffness along the directions of [111] and [100], respectively. Unlike CsK2Bi, CsNa2Bi exhibits almost isotropic elastic behavior at zero pressure. We found that hydrostatic tension and compression change the isotropic and anisotropic mechanical responses of these compounds. Moreover, the auxetic nature of the CsK2Bi compound is tunable under pressure. This compound transforms into a material with a positive Poisson’s ratio under hydrostatic compression, while it holds a large negative Poisson’s ratio of about −0.45 along the [111] direction under hydrostatic tension. An auxetic nature is not observed in CsNa2Bi, and Poisson’s ratio shows completely isotropic behavior under hydrostatic compression. A directional elastic wave velocity analysis shows that hydrostatic pressure effectively changes the propagation pattern of the elastic waves of both compounds and switches the directions of propagation. Cohesive energy, phonon dispersion, and Born–Huang conditions show that these compounds are thermodynamically, mechanically, and dynamically stable, confirming the practical feasibility of their synthesis. The identified mechanisms for controlling the auxetic and anisotropic elastic behavior of these compounds offer a vital feature for designing and developing high‐performance nanoscale electromechanical devices. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
Publication Date: 2021
Physica E: Low-Dimensional Systems and Nanostructures (13869477)127
In this work, some physical properties of ScX (X = Sb and Bi) nano-layers are evaluated based on DFT employing Wien2k code within generalized gradient approximation in presence of spin orbit coupling. The band order and topological phase of ScX (X = Sb, Bi) bulks are investigated and then the topological nature of these bulks is examined by the investigation of surface states topological phase of ScX nano-layers with different thicknesses. The bonding type between the surface atoms of ScX nano-layers is also investigated. Furthermore, the optical properties of ScX nano-layers are investigated and compared. The results show the high contribution of intraband transitions and consequently high reflectivity and negative real part of dielectric function of these nano-layers near zero energy. The different responses of ScX nano-layers to the radiated electromagnetic waves in polarizations of parallel and perpendicular to their surfaces imply the anisotropic optical features of these nano-layers in x (or y) and z directions. © 2020 Elsevier B.V.
Publication Date: 2020
Journal of Physics and Chemistry of Solids (00223697)145
In this study, we investigated some physical properties of AB (A = Sc, Y and B = Sb, Bi) compounds in different structural phases based on density functional theory. The effects of different hydrostatic pressures and biaxial strains on the band orders of AB compounds were investigated. The calculations were conducted with the Wien2k package in the presence of spin orbit coupling. The results showed that the topological d-p band inversion can be induced by appropriate compressive strains and spin orbit coupling. The topological phase of AB compounds was confirmed based on calculations of the Z2 topological invariant. The band inversions and strong topological phases of these compounds may make them suitable for appropriate applications in quantum computation and spintronics. Furthermore, we investigated and compared the optical properties of AB compounds, and the results indicated the high contributions of intraband transitions, high reflection, and negative real part of the dielectric function for these compounds near zero energy. © 2020 Elsevier Ltd
Publication Date: 2020
Journal of Physics and Chemistry of Solids (00223697)143
The structural, electronic, optical and elastic properties of CsCdxPb1−xCl3alloys are studied using the plane-wave pseudopotential method under the framework of density functional theory (DFT). The Perdew–Burke–Ernzerhof functional (GGA−PBE)is employed to treat the exchange and correlation potentials. The supercell approach (SC)and the virtual crystal approximation (VCA)are also used to model the CsCdxPb1−xCl3alloys. Because of the symmetry constraint in the VCAapproach, the calculated lattice parameters of these alloys only within SCapproach show linear behavior in agreement with the Vegard's law. Using the approach of Zunger and co-workers, the microscopic origin of the energy band gap bowing of these alloys is investigated in terms of the volume deformation, charge exchange and structural relaxation. The energy band gap of these alloys is also predicted to be suitable for solar absorber applications. The real and imaginary parts of the macroscopic dielectric function (MDF)of CsCdxPb1−xCl3alloys are studied using the single-particle picture within random phase approximation (RPA). The calculated static dielectric constant of these alloys increases when Cdconcentration decreases. To study the excitonic effects (EXC), the macroscopic dielectric function of these alloys is also calculated through the solution of the Bethe-Salpeter equation (BSE)using Tamm-Dancoff approximation within many-body perturbation theory. The variation of some polycrystalline structural properties of these alloys such as the Bulk modulus, Young's modulus, Poisson's ratio, Pugh's ratio, shear and Zener's anisotropy parameters as a function of the Cdconcentration are studied using perturbation density functional theory (PDFT). The calculated results show that these alloys are mechanically stable and rather elastically anisotropic. This study provides a detailed theoretical analysis of the CsCdxPb1−xCl3alloys and can give helpful guidance for further relevant research. © 2020
Publication Date: 2020
Journal of Physics Condensed Matter (09538984)32(25)
Topological insulators with novel surfaces or edge states are the topological nature sequel of bulk electronic wave functions of these materials. The observed signatures in the electronic structure of topological insulators can make them excellent candidates for thermoelectric materials. Low dimensional materials such as phosphorene and Bi2Te3 nanowire have been confirmed to be desirable for the design of devices with high thermoelectric performance. So in this work, the phonon modes, formation energy and cohesive energy of LaX (X = Sb, Bi) monolayers are first calculated and investigated. Then the band order of these monolayers is investigated by the band structure calculations and the topological phase of these monolayers is proved by using the calculation of Z 2 topological invariant. The energy band gap and the band inversion strength of these monolayers are evaluated under in-plane strains. Also, the effect of different temperatures and in-plane strains on the thermoelectric performance of LaX monolayers is studied. The results show the high thermoelectric efficiency and d-p topological band inversion of these monolayers under compressive strains. © 2020 IOP Publishing Ltd.
Publication Date: 2020
Journal of Magnetism and Magnetic Materials (03048853)503
Based on ab initio calculations, we have studied structural, electronic and optical properties of MoX2(X = S, Se) metal dichalcogenides and their nano-layers (NLs) according to the density functional theory using Wien2k code. The generalized gradient approximation (GGA) and GGA Engel-vosko are adopted to perform the exchange-correlation calculations. The equilibrium lattice parameters of MoS2 and MoSe2 compounds are calculated. The mechanical stability of these compounds is proved using Born condition. Moreover, the ductility and brittleness of MoX2 compounds are studied. The topological phase of MoS2 and MoSe2 bulks and their NLs is studied utilizing band order, Z2 invariant and surface density of states. The optical properties of MoX2 bulks and NLs are studied. The Penn model is satisfied for both MoS2 and MoSe2 compounds by studying their real part of static dielectric function. The increase of the thickness of these NLs leads to the changes in the absorption, reflectivity and energy loss function of these NLs in some specific energy ranges. © 2020 Elsevier B.V.
Publication Date: 2019
Journal of Electronic Materials (03615235)48(12)pp. 7977-7990
The Born effective charge tensors, high-frequency dielectric constants, phonon frequencies at Г symmetry point, and phonon dispersion curves of MoS2xSe2(1−x) (x = 0, 0.25, 0.5, 0.75, and 1) alloys are calculated based on density functional perturbation theory using optimized lattice parameters. The structural stability, stiffness, ductility, and plasticity of these alloys are explored in detail by calculating the polycrystalline structural properties. The calculated Born effective charges and Poisson’s ratio indicate the existence of a combination of ionic and covalent bonding between the transition metal and chalcogens in each layer. Based on the calculated phonon frequencies, the temperature dependence of the specific heat at constant volume, entropy, and Helmholtz free energy of MoS2xSe2(1−x) (x = 0, 0.25, 0.5, 0.75, and 1) alloys are calculated in the harmonic approximation. Structurally, the spatial inversion symmetry in the MoS2xSe2(1−x) (x = 0.25, 0.5, and 0.75) alloys is broken. This leads MoS2xSe2(1−x) (x = 0.25, 0.5, and 0.75) alloys to exhibit novel nonlinear optical properties that do not exist in the 2H-MoX2 (X = S, Se) compounds. So, the nonlinear optical properties are calculated by applying the 2n + 1 theorem to an electric-field-dependent energy functional. It is found that MoS2xSe2(1−x) (x = 0.25, 0.5, and 0.75) alloys exhibit remarkable large nonlinear optical susceptibility and electro-optic coefficients and would be promising candidates for use in nonlinear optical applications. Van der Waals interactions are included in all the first-principles calculations, to correctly describe the interaction between adjacent layers. The calculated lattice parameters, electronic energy bandgaps, phonon frequencies, and high-frequency dielectric constants of 2H-MoX2 (X = S, Se) compounds are in good agreement with available theoretical and experimental results. © 2019, The Minerals, Metals & Materials Society.
Publication Date: 2019
Indian Journal of Physics (09731458)93(11)pp. 1427-1436
The WIEN2K package based on the density functional theory within the generalized gradient approximation (GGA) and GGA plus Hubbard parameter was applied to explore the structural, electronic, magnetic properties and topological phase of CeNiSb bulk and nano-layer (NL), in the presence of spin orbit coupling. Also the topological phase, band order and the linear coefficient of electronic specific heat of CeNiSb bulk and nano-layer are studied. The electronic charge distribution at this nano-layer surface, within GGA and GGA + U approaches, is calculated. © 2019, Indian Association for the Cultivation of Science.
Publication Date: 2019
Computational Condensed Matter (23522143)19
The first principle investigations of the structural, electronic, linear and nonlinear response properties of the zinc-blende ZnSe and ZnTe are performed based on the density functional theory using a plane-wave pseudopotential approach. The Born effective charges, piezoelectric tensor, phonon frequencies, LO–TO splitting and thermal properties of these compounds are calculated using a linear response method within the density functional theory framework. The macroscopic dielectric function is calculated in the response of the many body effects within the Bethe-Salpeter approach using the Tam-Dancoff approximation. The nonlinear response properties to atomic displacements and electric fields are investigated within the density functional perturbation theory framework based on the 2n+1 theorem as implemented by the ABINIT software. After the calculation of the Kohn–Sham electronic band structures, the correction of the energy band gap is computed using the GW approximation within the many-body perturbation theory framework (MBPT). The results are in excellent agreement with the available experimental and other theoretical results. © 2019 Elsevier B.V.
Publication Date: 2019
Solar Energy (0038092X)184pp. 372-377
On the basis of density functional calculations and using Bader's atom in molecule theory, this article presents quantitative microscopic analyses on the bonding properties of amorphous silicon (a-Si) which could reflect in the observable mechanical and electronic behaviors of this material. In addition, the occurrence and strength of quantum confinement of charge carriers in a composition of silicon crystal nano slabs (SiNSs) embedded in hydrogenated a-Si (a-Si:H) semiconductor are studied. It is shown that the strongest confinement effect happens for Si slabs limited in [1 0 0] direction. The band gap tunability with the width of SiNSs is exhibited and a scaling law is investigated for the size dependent behavior of energy states. It is demonstrated and argued why in these systems the confinement of holes is stronger than electron confinement. The computational methodology used to passivate a-Si defects by hydrogen is also detailed. © 2019
Publication Date: 2019
Indian Journal of Physics (09731458)93(5)pp. 571-582
Our previous study of XFeSi (X = La, Gd, Tb) bulks shows that Fe atom has negligible contribution to the magnetic properties of these compounds. In this paper, the contribution of Fe atom to the magnetic properties of XFeSi (X = La, Gd, Tb) nano-layers is investigated. The calculated results are performed based on the density functional theory. The exchange–correlation potential is calculated using generalized gradient approximation and generalized gradient approximation plus Hubbard parameter. The structural, electronic and magnetic properties of XFeSi (X = La, Gd, Tb) nano-layers are investigated in the presence of spin–orbit coupling. The calculated results are compared with the corresponding results of their bulks. Furthermore, the thermodynamic properties of these nano-layers are investigated using the quasi-harmonic Debye model. The bulk modulus, Debye temperature, specific heat at constant pressure and volume and thermal expansion coefficient of these nano-layers are calculated and compared with the corresponding results of their bulks. © 2018, Indian Association for the Cultivation of Science.
Publication Date: 2019
Physics Letters, Section A: General, Atomic and Solid State Physics (03759601)383(2-3)pp. 221-230
First principle calculations have been employed to investigate the effects of Y concentration, pressure and temperature on various properties of Gd1−xYxAuPb (x=0,0.25,0.5,0.75,1) alloys using density functional theory (DFT). The full potential linearized augmented plane wave (FP-LAPW) method within a framework of the generalized gradient approximation (GGA) is used to perform the calculated results of this paper. Phase stability of Gd1−xYxAuPb alloys is studied using the total energy versus unit cell volume calculations. The equilibrium lattice parameters of these alloys are in good agreement with the available experimental results. The mechanical stability of Gd1−xYxAuPb alloys is proved using elastic constants calculations. Also, the influence of Y concentration on elastic properties of Gd1−xYxAuPb alloys such as Young's modulus, shear modulus, Poisson's ratio and anisotropy factor are investigated and analyzed. By considering both Pugh's ratio and Poisson's ratio, the ductility and brittleness of these alloys are studied. In addition, the total density of states and orbital's hybridizations of different atoms are investigated and discussed. Moreover, the effect of pressure and temperature on some important thermodynamic properties is investigated. © 2018 Elsevier B.V.
Publication Date: 2018
Journal of Alloys and Compounds (09258388)768pp. 433-440
In this paper, the topological phase of LuX (X = Sb, Bi) compounds under hydrostatic and biaxial pressures is investigated based on first principles of density functional theory by WIEN2k package. To find out the Z2 topological invariants of centrosymmetric compounds with the time reversal symmetry, the Bloch functions parity analysis can be used via electronic band structure calculations. So in this paper the Z2 topological invariants of the LuX (X = Sb, Bi) compounds with the time reversal and inversion symmetries are calculated using this approach. The results show that the d-p band inversion can be occurred in these compounds due to spin orbit interaction and appropriate pressure. These compounds have the strong electronic interaction due to their large d-electronic orbitals near the Fermi energy. The dynamic stability of these compounds is verified by phonon modes analysis. The surface states topological phase of these compounds are investigated based on the band structure calculations. © 2018 Elsevier B.V.
Publication Date: 2018
Physical Review B (24699950)98(12)
Based on density functional simulations combined with the Landauer transport theory, the mechanical strain impacts on the chemical bonds of phosphorene and their effects on the electronic properties are studied. Moreover, the effect of the tensile strain along the zigzag direction on the charge transport properties of a two-terminal phosphorene device is evaluated. Enhancement of the intraplanar interactions, in particular between the next-nearest neighbors in strained phosphorene, is found to be essential in the band-structure evolution. The charge transport analyzing shows that phosphorene has a strong piezoconductance sensitivity, which makes this material highly desirable for high-pressure nanoelectromechanical applications. The piezoconductance gauge factor increases by strain from 46 in 5% tension to 220 in 12% tension, which is comparable to state-of-the-art silicon strain sensors. The transmission pathways monitor the current flowing in terms of the chemical bonds and hopping, however, the transport mostly arises from the charge transferring through the chemical bonds. The strong anisotropy in the transport properties along zigzag and armchair directions is observed. © 2018 American Physical Society.
Publication Date: 2018
European Physical Journal B (14346028)91(7)
In this study, Kondo behavior, electronic structure and magnetic properties of CeRuPO-nano-layer are investigated using the first principles calculations. The calculations are performed by employing the full potential linearized augmented plane wave (FP-LAPW) method based on the density functional theory (DFT). These properties are calculated in the presence of spin-orbit interaction. The exchange-correlation interaction is calculated within generalized gradient approximation (GGA). In addition, the GGA+U approach (where U is the Hubbard correlation term) is also employed to improve treatment of the f-electrons. The calculated partial electron density of states demonstrates that the hybridization between Ce-4f and Ru-5d orbitals and consequently Kondo effect changes at the surface of the CeRuPO-nano-layer compared to the bulk. The results show that due to the weaker Kondo effect at the surface of CeRuPO-nano-layer, the magnetic moment of Ce atoms enhances and the effective mass of the conduction electron reduces. © 2018, EDP Sciences, SIF, Springer-Verlag GmbH Germany, part of Springer Nature.
Publication Date: 2018
Physical Review B (24699950)97(23)
The effects of lattice distortion and chemical disorder on charge transport properties of two-terminal zigzag phosphorene nanoribbons (zPNRs), which shows resonant tunneling behavior under an electrical applied bias, are studied. Our comprehensive study is based on ab initio quantum transport calculations on the basis of the Landauer theory. We use nitrogen and silicon substitutional dopant atoms, and employ different physical quantities such as the I-V curve, voltage drop behavior, transmission spectrum, transmission pathway, and atomic current to explore the transport mechanism of zPNR devices under a bias voltage. The calculated transmission pathways show the transition from a ballistic transport regime to a diffusive and in some particular cases to localized transport regimes. Current flowing via the chemical bonds and hopping are monitored; however, the conductance originates mainly from the charge traveling through the chemical bonds in the vicinity of the zigzag edges. Our results show that in the doped systems, the device conductance decreases and the negative differential resistance characteristic becomes weak or is eliminated. Besides, the conductance in a pure zPNR system is almost independent of the ribbon width. © 2018 American Physical Society.
Publication Date: 2018
Journal of Superconductivity and Novel Magnetism (15571947)31(5)pp. 1515-1525
The structural, electronic, magnetic, and optical properties of Mn-based Heusler Mn2ZrGa1−xGex (x = 0, 0.25, 0.5, 0.75, and 1) alloys are calculated by first-principles full-potential linearized augmented plane wave plus local orbital (FP-LAPW+lo) method. It is found that Mn2ZrGa1−xGex alloys are half-metallic ferrimagnetic and their magnetic moments are in good agreement with the Slater–Pauling relationship. The calculations reveal that all alloys have a pseudo-gap in the majority-spin channel except for x = 0.75 and x = 1 which have a real gap in the majority-spin channel. The spin polarization is quite large for whole series, and it reaches to a value of 100% for x = 0.75 and x = 1. Our calculated results clearly show that with the Ge substitution, the lattice parameter linearly decreases while the bulk modulus increases. Moreover, the calculated formation energies confirm that these alloys are stable chemically. The optical properties, including the real and imaginary parts of the dielectric function, reflectivity, and absorption spectra, were also investigated. The results show that the dominant behavior, at energy below 1 eV, is due to interactions of free electrons in the system. The increment of Ge concentration leads to an increase in the plasma frequency of metallic spin channel. © 2017, Springer Science+Business Media, LLC.
Publication Date: 2018
Journal of Magnetism and Magnetic Materials (03048853)451pp. 681-687
Topological phase of Gd1−xYxAuPb (x = 0, 0.25, 0.5, 0.75, 1) alloys have been studied utilizing density function theory by WIEN2k code. The generalized gradient approximation (GGA), generalized gradient approximation plus Hubbard parameter (GGA + U), Modified Becke and Johnson (MBJ) and GGA Engel-vosko in the presence of spin orbit coupling have been used to investigate the topological band structure of Gd1−xYxAuPb alloys at zero pressure. The topological phase and band order of these alloys within GGA and GGA + U approaches under hydrostatic pressure are also investigated. We find that under hydrostatic pressure in some percentages of Gd1−xYxAuPb (x = 0, 0.25, 0.5, 0.75, 1) alloys in both GGA and GGA + U approaches, the trivial topological phase is converted into nontrivial topological phase. In addition, the band inversion strength versus lattice constant of these alloys is studied. Moreover, the schematic plan is represented in order to show the trivial and nontrivial topological phase of Gd1−xYxAuPb (x = 0, 0.25, 0.5, 0.75, 1) alloys in both GGA and GGA + U approaches. © 2017 Elsevier B.V.
Publication Date: 2018
Journal of Superconductivity and Novel Magnetism (15571947)31(1)pp. 209-216
The structural, electronic, and magnetic properties of Nd1−xLaxFeSi (x = 0, 0.25, 0.50, 0.75, and 1) alloys are investigated based on the first-principle density functional theory by using the full-potential linear muffin-tin orbital (FP-LMTO) method. The exchange-correlation potential is treated with local density approximation (LDA). In addition, to treat localization of 4f-electrons properly, the LDA + U approach (where U is the Hubbard correlation term) is also employed. The calculated structural, electronic, and magnetic properties of these alloys within LDA and LDA + U approaches are compared. The calculated lattice constants of these alloys as a function of x within the LDA + U approach are in the best agreement with linear Vegard’s rule. Most importantly, we focus on the magnetic properties of these alloys and find that the magnetic interaction between Nd atoms is the Rudermen-Kittel-Kasuya-Yosida (RKKY) interaction type. Iron does not carry magnetic moment in these alloys and has just an induced small magnetic moment from Nd atoms. © 2017, Springer Science+Business Media New York.
Publication Date: 2017
Journal of Superconductivity and Novel Magnetism (15571947)30(8)pp. 2143-2158
The structural, electronic, magnetic, and thermodynamic properties of XFeSi (X = Gd, Tb, La) and GdRuSi compounds are investigated using density functional theory by the WIEN2k code. Using the first-principle procedure, the Hubbard parameter of Gd and Tb 4f electrons and La 5d electrons of XFeSi (X = Gd, Tb, La) and GdRuSi compounds is calculated. The structural and electronic and magnetic properties of these compounds within GGA and GGA + U approaches in the presence of spin-orbit coupling are calculated and compared. The calculated results indicate that the ferromagnetic phase is the most stable phase of XFeSi (X = Gd, Tb) and GdRuSi compounds and the nonmagnetic phase is the stable phase of LaFeSi. The magnetic moment of GdFeSi, GdRuSi, and TbFeSi compounds is due to Gd and Tb atoms. The calculated electronic band structures of these compounds show that these compounds have metallic behavior. Furthermore, the thermodynamic properties of these compounds using the quasi-harmonic Debye model as a function of temperature and pressure within GGA and GGA + U approaches are investigated. © 2017, Springer Science+Business Media New York.
Publication Date: 2017
Thin Solid Films (00406090)634pp. 112-120
The topological phase and optical properties of LuNiBi bulk and nano-layer are studied. The self-consistent calculations are carried out in presence of spin-orbit coupling, based on density functional theory using generalized gradient approximation, local density approximation, Engle-Vosco generalized gradient approximation and modified Becke and Johnson potential. The effect of hydrostatic and uniaxial pressures on band order, energy band gap and optical properties of LuNiBi compound is investigated within different approaches. The topological phase of surface states and the optical properties of LuNiBi nano-layer are studied. The results show that the topological phase and energy gap of LuNiBi bulk and nano-layer are sensitive to pressure and type of exchange-correlation potential. There is an anisotropic response of LuNiBi nano-layer to the incident electromagnetic waves polarizations, parallel and perpendicular to the nano-layer surface. © 2017 Elsevier B.V.
Publication Date: 2017
Journal of Magnetism and Magnetic Materials (03048853)434pp. 62-67
The electronic, magnetic and optical properties of X-doped ScPdBi (X = Gd, Np, Cm) are investigated in the framework of density functional theory. The exchange-correlation potential is treated using generalized gradient approximation with Coulomb interaction parameter. The band order and energy band gap of X-doped ScPdBi are investigated by calculation of band structure. The effect of doping impurity on magnetic properties of ScPdBi compound is studied by calculation of total and partial magnetic moments of X-doped ScPdBi compound. Furthermore, the optical properties of X-doped ScPdBi are calculated and compared in the energy range of 0–25 eV. © 2017
Publication Date: 2017
Journal of Magnetism and Magnetic Materials (03048853)426pp. 287-293
The structural, electronic and magnetic properties and Kondo behavior of Ce1−xLaxRuPO(x=0, 0.25, 0.5, 0.75 and 1) alloys are investigated using density functional theory by utilizing Wien2k package. The exchange-correlation potential is treated with the generalized gradient approximation (GGA). Moreover, the GGA+U approach (where U is the Hubbard correlation term) is employed to treat the f-electrons properly. We also present a comparative study between the electronic structure and magnetic properties of these alloys within GGA and GGA+U approaches. The calculated lattice parameters and bulk moduli of these alloys as a function of x are in the best agreement with Vegard's linear rule. The total and partial electron density of states and linear coefficient of electronic specific heat of these alloy within GGA and GGA+U are investigated and compared. The effect of La substitution on the Kondo behavior of CeRuPO compound is investigated. © 2016 Elsevier B.V.
