Effect of Strain on the Electronic Structure and Phonon Stability of SrBaSn Half Heusler Alloy (original) (raw)
Related papers
Chinese Journal of Physics, 2018
A theoretical study of magnetic, electronic, mechanic, anisotropic elastic, and vibrational properties of Ru 2 TGa (T = Cr, Mn, and Co) Heusler alloys has been extensively investigated by the first-principles method using the generalized gradient approximation. Structural parameters such as lattice constant (a 0), bulk modulus (B) and first pressure derivative of bulk modulus (B¢) were obtained by using the Murnaghan equation. The calculated formation enthalpies (DH f) showed that these alloys are thermodynamically stable. The total spin magnetic moments per unit cell of Ru 2 TGa (T = Cr, Mn, and Co) alloys were found to be 1.16 l B , 2.16 l B and 0.29 l B , respectively. In addition to electronic band structures along the high symmetry directions, corresponding total and partial density of states were also plotted. It was found that the spin-up states have a metallic character for all alloys, but the spin-down states of the other alloys except for Ru 2 CoGa have a pseudo-gap at the Fermi level. The bulk modulus (B), shear modulus (G), ratio of B/G, Young's modulus (E), Poisson's ratios (m), Vickers hardness (H V), sound velocities (v l , v t , and v m), Debye temperatures (H D) and melting temperatures (T melt) were obtained from elastic constants (C ij) in accordance with the Voigt-Reuss-Hill approximation. The calculated elastic constants showed that these alloys are mechanically stable and they have anisotropic character. The elastic anisotropy of the considered alloys was analyzed and pictured in great detail with 2D and 3D figures of directional dependence of Young's modulus, linear compressibility, shear modulus, and Poisson's ratio.These alloys are dynamically stable because there are no negative modes in their phonon dispersion curves.
Computational Materials Science, 2015
Structural, elastic, thermodynamic, electronic, and magnetic properties of the full-Heusler compound Ag 2 CeAl were determined using generalized gradient approximation with exchange-correlation functional GGA (PBEsol) with spin-orbit coupling (SOC) correction. The elastic modulus and their pressure dependence are calculated. From the elastic parameter behavior, it is inferred that this compound is elastically stable and ductile in nature. Through the quasi-harmonic Debye model, in which the phononic effect is considered the effect of pressure P (0 to 50) and temperature T (0 to 1000) on the lattice constant, the elastic parameters, bulk modulus B, heat capacity and thermal expansion α, internal energy U , entropy S, Debye temperature θ D , Helmholtz free energy A, and Gibbs free energy G are investigated. The thermodynamic properties show that the compound Ag 2 CeAl is a heavy fermion material. The density of state (DOS), magnetic momentum, and band structure are computed, to investigate the magnetic and metallic characteristics. The calculated polarization of the compound is 77.34%. The obtained results are the first predictions of the physical properties for the rare-earth-based (Ce) full-Heusler Ag 2 CeAl.
Journal of Electronic Materials
A theoretical study of magnetic, electronic, mechanic, anisotropic elastic, and vibrational properties of Ru 2 TGa (T = Cr, Mn, and Co) Heusler alloys has been extensively investigated by the first-principles method using the generalized gradient approximation. Structural parameters such as lattice constant (a 0), bulk modulus (B) and first pressure derivative of bulk modulus (B¢) were obtained by using the Murnaghan equation. The calculated formation enthalpies (DH f) showed that these alloys are thermodynamically stable. The total spin magnetic moments per unit cell of Ru 2 TGa (T = Cr, Mn, and Co) alloys were found to be 1.16 l B , 2.16 l B and 0.29 l B , respectively. In addition to electronic band structures along the high symmetry directions, corresponding total and partial density of states were also plotted. It was found that the spin-up states have a metallic character for all alloys, but the spin-down states of the other alloys except for Ru 2 CoGa have a pseudo-gap at the Fermi level. The bulk modulus (B), shear modulus (G), ratio of B/G, Young's modulus (E), Poisson's ratios (m), Vickers hardness (H V), sound velocities (v l , v t , and v m), Debye temperatures (H D) and melting temperatures (T melt) were obtained from elastic constants (C ij) in accordance with the Voigt-Reuss-Hill approximation. The calculated elastic constants showed that these alloys are mechanically stable and they have anisotropic character. The elastic anisotropy of the considered alloys was analyzed and pictured in great detail with 2D and 3D figures of directional dependence of Young's modulus, linear compressibility, shear modulus, and Poisson's ratio.These alloys are dynamically stable because there are no negative modes in their phonon dispersion curves.
2022
First-principles calculations has led to significant discoveries in materials science. Half-Heusler (HH) alloys, which are potential thermoelectric materials have demonstrated significant improvements in thermoelectric performance owing to their thermal stability, mechanical strength, and moderate ZT. Using Density functional theory (DFT), the structutal, mechanical, electronic, and lattice dynamical properties of cubic Half-Heusler Alloys ZrCoY (Y=Sb,Bi) have been investigated. The unknown exchange-correlation functional is approximated using the generalized gradient approximation (GGA) pseudopotential plane wave approach. The structural parameters, that is, equilibrium lattice constant, elastic constant and its derivative are consistent with reported experimental and theoretical studies where available. Mechanical properties such as anisotropy factor A, shear modulus G, bulk modulus B, Young's modulus E, and Poison's ratio n are calculated using the Voigt-Reuss-Hill average approach based on elastic constants. Debye temperature, as well as longitudinal and transversal velocities are predicted from elastic constants at GGA-PBE and GW levels of theory. The study of elastic constants showed that the compounds are mechanically stable, and the phonon dispersion study showed that they are dynamically stable as well. The ductility and anisotropic nature of the compounds were also confirmed by the elastic constants and mechanical properties.
VNU Journal of Science: Mathematics - Physics
Half-Heusler (hH) alloys are an intriguing class of materials with significant potential for applications in spintronics, thermoelectrics, optoelectronics, and magnetoelectronics due to their unique adjustable properties. In this work, we have investigated the structural, thermodynamic, mechanical, and electronic properties of RuVZ (Z: As, Bi, Sb) half-Heusler materials using the density functional theory (DFT) as implemented in the quantum espresso computational suite. The structural, thermodynamic, and mechanical properties were also predicted using the linear response density functional perturbation theory. We observed that the hH alloys are non-magnetic semiconductors and have an indirect narrow band gap. The band gap values and lattice constants for RuVSb and RuVAs cubic crystals are consistent with published reports. RuVBi has a lattice constant of 6.18 and a band gap of 0.16 eV. The elastic parameter results obtained satisfy Born's stability requirements, suggesting mec...
Structural and lattice dynamical study of half Heusler alloys RuMnX (X = P, As)
PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS: ICAM 2019, 2019
In this report, we have investigated the structural and lattice dynamical properties of Half Heusler alloys RuM nX (X=P, As) under the framework of first principles calculations. The structural parameters such as lattice constants have been calculated and found to be in good agreement with the available theoretical results, while bulk modulus and pressure derivative of bulk modulus has been reported for the first time. A linear response approach of density functional perturbation theory has been employed for the calculations of lattice dynamics of these alloys. The calculated phonon dispersion curve (PDC) does not show any imaginary frequency in any symmetric directions, indicating the stability of alloys in the cubic phase. All the phonon frequencies corresponding to acoustical and optical phonon modes have been assigned. Comparison of PDC of both alloys reveal that the phonon gap has been found to be more in RuM nAs than in RuM nP. Lattice dynamical properties for these alloys has been reported for the first time. The phonon density of states for both alloys have also been calculated.
Lattice dynamics, mechanical stability and electronic structure of Fe-based Heusler semiconductors
Scientific Reports, 2019
The structural and mechanical stability of Fe2TaAl and Fe2TaGa alloys along with the electronic properties are explored with the help of density functional theory. On applying different approximations, the enhancement of semiconducting gap follows the trend as GGA < mBJ < GGA + U. The maximum forbidden gaps observed by GGA + U method are Eg = 1.80 eV for Fe2TaAl and 1.30 eV for Fe2TaGa. The elastic parameters are simulated to determine the strength and ductile nature of these materials. The phonon calculations determine the dynamical stability of all these materials because of the absence of any negative frequencies. Basic understandings of structural, elastic, mechanical and phonon properties of these alloys are studied first time in this report.
The density functional theory was used to explore the structural, electronic, dynamical, and thermoelectric properties of a VIrSi Half-Heulser (HH) alloy. The minimum lattice constant of 5.69 ( ̊A) was obtained for VIrSi alloy. Besides, the band structure and the projected density of states for this HH alloy were calculated, and the gap between the valence and conduction bands was noted to be 0.2 eV. Also, the quasi-harmonic approximation was used to predict the dynamical stability of the VIrSi HH alloy. At 300 K, the Seebeck Coefficient of 370 and -270 μV.K−1., respectively, was achieved for the p and n-type doping. From the power factor result, the highest peak of 18 X 1011W/cm.K2 is obtained in the n-type doping. The Figure of Merit (ZT) result revealed that VIrSi alloy possesses a high ZT at room temperature, which would make VIrSi alloy applicable for thermoelectric performance.
Journal of the Korean Physical Society, 2020
In the present study, the second-order elastic constants and the electronic band structures of the X2ScAl (x = Ir, Os, and Pt) compounds crystallized in the L21 phase were calculated separately by using the ab-initio density functional theory. According to the results for the second-order elastic constants, these compounds met the Born mechanical stability criteria. Also, according to the Pugh criteria, they were found to have a ductile structure and to show anisotropic behavior. The microhardneses of the compounds were between 2 and 14 GPa, and the highest hardness was found in the Ir2ScAl (14.290 GPa) compound. In addition, the energy band structures of these compounds were calculated, and the crystals were found to have a metallic bond structure. All the computed data were compared with previously calculated results obtained with different methods. According to the findings obtained in the present study, in terms of its mechanical and electronic behaviors, Ir2ScAl was found to have better physical properties than Os2ScAl and Pt2ScAl. The phonon dispersion curves and their corresponding total and projected densities of states were investigated for the first time by using a linear-response approach in the context of density functional perturbation theory. The frequencies of the optical phonon modes of all compounds at the Γ point were 4.767, 7.504 and 9.271 THz for Ir2ScAl, 2.761, 7.985 and 9.184 THz for Os2ScAl and 2.012, 5.6952 and 8.118 THz for Pt2ScAl. The heat capacity Cv at constant volume versus temperature was calculated using a quasi-harmonic approach and the results are discussed.
Heusler Alloys: Structural, Electronic, Magnetic, Mechanical, and Thermoelectric Features - A Review
International Journal of Advanced Science and Engineering, 2024
This review paper presents an in-depth analysis of Heusler alloys, focusing on their structural, electronic, magnetic, mechanical, and thermoelectric characteristics, and potential applications. It begins with an examination of the crystal structure and composition, highlighting how composition influences structural properties. The paper delves into the electronic aspects by analyzing band structures and Fermi surfaces through density functional theory studies. The magnetic behavior of these alloys, pivotal in spintronic applications, is also scrutinized. Furthermore, the paper discusses mechanical properties like elastic constants and shape memory effects, and thermoelectric features including phonon and electron transport. Applications in energy conversion, storage, spintronics, sensing, and actuation are explored, emphasizing the alloys' role in lithium-ion batteries, fuel cells, spin valves, and magnetic tunnel junctions. Finally, it addresses challenges and future perspectives in synthesizing and integrating Heusler alloys for enhanced performance, underscoring the need for further research to unlock their full potential in various technological fields.