half-Heusler Alloys Research Articles

First-principles study of structural, elastic, mechanical, electronic, magnetic, optical, and thermoelectric properties of CoFeTe half-heusler alloy

Half-Heusler CoFeTe alloy is analyzed using Density Functional Theory (DFT) calculations based on the GGA-PBE and GGA + U approximations. The results reveal that CoFeTe was most stable in the β-phase with a ferromagnetic configuration. As determined by the density of states analysis, metallic behavior is observed for the GGA-PBE approximation, whereas a semi metallic nature is observed for the GGA + U approximation. Phonon dispersion, elastic, and mechanical analyses confirm the dynamical and mechanical stability of the alloy. The thermoelectric properties suggest that CoFeTe shows potential for thermoelectric applications, with an increasing Seebeck coefficient and power factor, reaching a ZT value of 0.2 at 800 K. These findings highlight the potential of CoFeTe for applications in thermoelectric devices.

First-principles calculations to investigate structural, electronic, magnetic mechanical, and thermal properties of half-Heusler alloys CoYGe (Y = Mn, Fe): using GGA and GGA+U potentials

First-principles calculations to investigate structural, electronic, magnetic mechanical, and thermal properties of half-Heusler alloys CoYGe (Y = Mn, Fe): using GGA and GGA+U potentials

Half-metallicity and thermoelectric performance: A multifaceted investigation of Zr-based half-Heusler alloys

This work employs the linearized augmented plane-wave (LAPW) method within the framework of density functional theory (DFT) to explore the structural, elastic, electronic, magnetic, and thermoelectric properties of the Zr-based half-Heusler alloys CoZrSn and CoZrPb. The exchange–correlation functional is treated using both the Perdew-Burke-Ernzerhof (GGA-PBE) generalized gradient approximation and the Tran-Blaha-modified Beck-Johnson (TB-mBJ) potential, as implemented in the WIEN2k software package. Our findings indicate that the investigated material exhibits mechanical stability, suggesting its potential for experimental synthesis. Furthermore, both CoZrSn and CoZrPb display half-metallic behavior consistent with Slater-Pauling’s rule, characterized by an integer magnetic moment of 1 μB. Electronic band structures and density of states calculations, employing the TB-mBJ approximation, confirm this half-metallic character. Notably, indirect band gaps of 0.52 eV and 0.69 eV are observed for CoZrSn and CoZrPb, respectively. To investigate thermoelectric properties, including the Seebeck coefficient (S), electrical conductivity (σ), thermal conductivity (κ), and figure of merit (ZT), the Boltzmann transport equations within the DFT framework were utilized. The calculated values for the figure of merit and Seebeck coefficient suggest that the CoZrX alloys hold promise for thermoelectric applications. Significantly, there is a lack of prior experimental or theoretical investigations on the CoZrX half-Heusler alloys. Consequently, our theoretical predictions regarding the structural, elastic, electronic, magnetic, and thermoelectric properties provide valuable insights that can be further validated through future experimental studies.

Systematic study of d0-d KYZ (Y = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Z = al, Ga, In, Si, Ge, Sn, Pb, P, As, Sb, Bi, S, Se, Te) Heusler alloys

The 126 half-Heusler alloys based on the KYZ (Y=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Z = Al, Ga, In, Si, Ge, Sn, Pb, P, As, Sb, Bi) in three different C1b structures (α, β and γ) have been investigated using Density Functional Theory. It was found that the α phase does not conserve cubic symmetry and its tetragonal ratio varies between 1.61 and 2.02. The α-type was shown to be energetically more favorable than the β and γ phases, which maintain cubic symmetry. Most of the studied phases were found to be mechanically unstable, but the 19 cubic phases were found to exhibit either semiconductor or half-metallic behavior with band gaps ranging between 0.48 and 3.18 eV. The calculated thermal lattice conductivity kL did not exceed 1.17 W/m·K, making these alloys promising as thermoelectric materials.

Topological signatures of triply degenerate fermions in Heusler alloys: an ab initio study

Triply degenerate nodal point (TP) fermions, lacking elementary particle counterparts, have been theoretically anticipated as quasiparticle excitations near specific band crossing points constrained by distinct space-group symmetries instead of Lorentz invariance. Here, based onfirst-principlescalculations and symmetry analysis, we demonstrate the presence of TP fermions in Heusler alloys. Furthermore, we predict that these Heusler alloys are dynamically stable, exhibiting TP fermions along four distinctC3axes in the F-43m space group. We show thatα-LiCaPdSb harbours peculiar Fermi arcs and surface states on the (111) and (001) crystal facets, owing to the coexistence of threefold rotational and time reversal symmetry. More interestingly, a modest tensile strain can increase the distance of fermions along the Γ-Lhigh symmetric line by as much as 21.10%, which give rise to measurable Fermi arcs. Furthermore, we investigate non-trivial topological insulator phase inβ-LiCaPdSb, by changing the chemical environment through placing transition metal atoms at various Wyckoff positions. Theβ-LiCaPdSb harbour a semi-metallic nature, and by breaking cubic symmetry, it undergoes a transition from semi-metal to a non-trivial topological insulator. In addition, for the first time, rare-earth LaPtBi half-Heusler alloy is examined under strain to uncover multiple band inversions associated with the TP fermionic phase. The observed multiple band inversion is entirely unaffected by spin-orbit coupling. We show that the LaPtBi compound hosts TP fermions, which are linked to aZ2topological invariant. Remarkably, with clear band crossings and multiple band inversion, we point out the possibilities of the LaPtBi for displaying a rich topological phase diagram. Our work provides a prototype material platform for experimental detection through angle-resolved photoemission spectroscopy or scanning tunnelling spectroscopy and practical spintronic applications.

Unveiling half-metallic, thermoelectric and optoelectronic behavior of the new Heusler alloy RbCrZ (Z = Si, Ge): a DFT perspective

Abstract Utilizing the density functional theory (DFT) method, this study aims to predict with precision the structural, elastic, electronic, magnetic, thermoelectric, thermal, and optical properties of two recently discovered half-Heusler alloys, namely RbCrSi and RbCrGe. The exchange and correlation potential are accounted for using the generalized gradient approximation of Perdew–Burke–Ernzerhof (GGA-PBE) and the Tran–Blaha-modified Becke–Johnson exchange potential (TB-mBJ). Through structural analysis, it is observed that both RbCrSi and RbCrGe alloys exhibit energetic stability in a type-3 structure with a ferromagnetic (FM) state. Both alloys exhibit half-metallic properties and integer magnetic moments of 3 μB, following the Slater-Pauli rule. Additionally, elastic calculations confirm their mechanical stability and anisotropic ductile behavior. The quasi-harmonic Debye model (QHDM) is employed for calculating thermodynamic properties, while the BoltzTraP code, based on semi-classical Boltzmann theory (SCBT), is utilized for evaluating thermoelectric properties. Findings reveal that RbCrZ alloys (with Z = Si, Ge) exhibit high figure of merit (ZT) values nearing unity at highest temperature. Consequently, the newfound half-Heusler alloys RbCrSi and RbCrGe hold significant promise for applications in thermoelectricity and spintronic devices. This comprehensive analysis underscores the potential of these alloys in the realm of renewable energy applications.

First-principles investigation of electronic, magnetic, and optical properties of FeMnSb/GaZ (Z = As or P) interfaces

We systematically investigated the electronic, magnetic, and optical properties of the FeMnSb half-Heusler alloy, its (001) surface, and its interfaces with GaAs and GaP semiconductors by using first-principles calculations based on density functional theory. The bulk FeMnSb reveals its half-metallic ferrimagnetism with 100% spin-polarization. Extending this study to the (001) surface, we uncover distinct electronic and magnetic behaviors for Fe- and MnSb-terminated surfaces, the MnSb-terminated surface preserving the half-metallicity observed in the bulk material. Our evaluation of the interfaces exhibits positive work of separation, indicating that these interfaces are energetically favorable. The density of states analysis reveals that all interfaces exhibit a metallic nature. High spin-polarization values, particularly 97.316% for the Fe-Ga interface, suggest a substantial degree of spin-polarized current. Notably, the absorption coefficient peaks shift from the ultraviolet (UV) region in the bulk alloy to the visible region at the (001) surfaces. However, at the FeMnSb/GaAs and FeMnSb/GaP interfaces, the highest absorption peaks revert to the UV region, highlighting strong interfacial coupling effects. These results suggest the tunability of FeMnSb optical properties via surface termination and interface engineering, making it a promising candidate for spintronic and optoelectronic applications.

Theoretical Insights into Off-Stoichiometric Zr(x)Ti(1-x)IrSb Half-Heusler Alloys: A First Principle Calculations.

This study presents a theoretical investigation into the phase stability, electronic, and optical properties of off-stoichiometric Zr_{x}Ti_{1-x}IrSb (x = 0, 0.0625, 0.1875, 0.25, 0.50, 0.75, 1) compounds. Using first-principles calculations, we explore how varying Zr and Ti concentrations can tune the electronic and optical properties of these half-Heusler alloys. The Structural, optical, and electronic properties were meticulously analyzed with both the GGA-PBE and Meta-GGA-SCAN approximations, as implemented in the Vienna Ab initio Simulation Package (VASP). The dynamical stability of these compounds was assessed using the Phonopy package. Our findings reveal that these alloys exhibit semiconductor behavior with tunable band gaps, and their optical properties show significant variation across different compositions, particularly in the visible light range. The compounds also demonstrate robust dynamical stability, indicating their potential for practical applications in electronic and optoelectronic devices. These results underscore the versatility of Zr_{x}Ti_{1-x}IrSb alloys and highlight their promise for next-generation technology.

Ferrimagnetic half metals TaMnZ (Z = As, Sb, Bi) for thermoelectric and spintronic applications – Material computations

Half metals possess coupling behavior of metals and semiconductors with wide heat transport and spin transport properties. This research article covers the structural, mechanical, electronic, magnetic and thermoelectric properties of the half Heusler alloys TaMnZ (Z = As, Sb, Bi). The equilibrium lattice constants and corresponding ground state energies show that the studied alloys are stable in the ferrimagnetic cubic phase. The band dispersion plots suggest that the compounds TaMnAs, TaMnSb and TaMnBi are half metals with indirect band gap having the band gap energies of 1.13 eV, 1.24 eV and 1.12 eV respectively in the spin down channel. As the materials have 100 % spin polarization with an integer magnetic moment of −1 μB, they are suitable for making spintronic devices such as spin transistors and spin-flip flops. The temperature-dependent thermoelectric properties of the alloys have been studied by classical Boltzmann theory. The materials have low lattice thermal conductivity which was confirmed by Slack’s equation. The obtained thermoelectric figure of merit for p-type TaMnAs, TaMnSb and TaMnBi is 0.7, 0.6 and 0.8 respectively at 1200 K. Similarly, the figure of merit obtained for n-type TaMnAs, TaMnSb and TaMnBi is 0.6, 0.64 and 0.8 respectively at the same temperature. The favourable heat and spin transport properties of these alloys show that they are the potential characters to figure out better thermoelectric and spintronic performance.

DFT study of structural, electronic, magnetic, elastic, and thermoelectric properties of Ta-based half-Heusler alloys CsTaX (X = C, Si, and Ge) for spintronics and thermoelectric technologies

The structural, electronic, elastic, magnetic, and thermoelectric characteristics of three novel Ta-based half-Heusler alloys, CsTaC, CsTaSi, and CsTaGe, have been investigated using the Full-Potential Linearized Augmented Plane Wave (FP-LAPW) method within the density functional theory (DFT). The volume-optimization graphs show that all compounds are stable in the ferromagnetic (FM) phase. Half-Metallicity of these compounds is confirmed by the density of states (DOS) and band structures. The total magnetic moment for CsTaC is 6 μB, and for CsTaX (X = Si, Ge) is 2 μB. The negative pd exchange energy and exchange constants confirm ferromagnetism. The values of Pugh’s ratio (B/G) and Poisson’s ratio (v) reveal that CsTaC is ductile and CsTaX (Si, Ge) is brittle. The thermoelectric response is estimated using the BoltzTraP code, demonstrating that at room temperature, maximum ZT values for CaTaC, CsTaSi, and CsTaGe are 0.99, 0.97, and 0.90, respectively. Consequently, CsTaX (X = C, Si, and Ge) are suitable candidates for spintronic and thermoelectric technologies.

First-principles calculations to investigate optoelectronic of transition-metal half-Heusler alloys MTiSn (M = Pd and Pt) for optoelectronics applications

The structural, mechanical, optical, and electronic properties of half-Heuslers MTiSn (M = Pd and Pt) are investigated using FP-LAPW incorporating the GGA-PBE. MTiSn crystallize in ferromagnetic (FM) and cubic structure (F-43m; C1b) with lattice constants of 6.216 Å and 6.241 Å, respectively, in good agreement with the available data. Elastic constants Cij reveal that MTiSn meet the mechanical stability criteria with notable thermodynamic properties. Also, we have conducted a detailed analysis of optical properties, encompassing the dielectric function, absorption coefficient, optical conductivity, optical refractivity, and extinction coefficient. It is found that PtTiSn shows higher optical responses than PdTiSn at low and high energy ranges. In terms of electronic properties, MTiSn demonstrate narrow bandgap semiconductor characteristics with an indirect bandgap of Eg = 0.507 eV (M = Pd) and Eg = 0.782 eV (M = Pt). The notable optoelectronic responses have also been examined, indicating the high potential of MTiSn materials for optoelectronic applications.

Optoelectronic and Thermoelectric Properties of Zirconium Half-Heusler Alloys RhZrX (X = P, As, Sb, Bi): an ab-initio Investigation

Optoelectronic and Thermoelectric Properties of Zirconium Half-Heusler Alloys RhZrX (X = P, As, Sb, Bi): an ab-initio Investigation

Tuning conduction properties and clarifying thermoelectric performance of P-type half-heusler alloys TiNi1−xCoxSn (0 ≤ x ≤ 0.15)

TiNiSn is an N-type thermoelectric material with a high-power factor composed of low toxicity and abundant elements. TiNiSn also shows P-type electrical conduction by hole doping. In this study, we tune the conduction properties of TiNi1−xCoxSn (0 ≤ x ≤ 0.15) with Co substitution at the Ni site. The samples were prepared by the arc melting method, and thermoelectric properties were investigated up to 800 K. The results of the Hall effect and the Seebeck coefficient measurements indicate that the majority of charge carriers changes from electrons to holes at x ≥ 0.03, suggesting that Co acts as an acceptor. We report for the first time that Ti0.994Ni1.00Co0.051Sn1.01 exhibits ZT = 0.12 at 675 K. This work reveals that Ti0.994Ni1.00Co0.051Sn1.01 could be a potential P-type thermoelectric material operating at high temperatures.

Alkali-based half metals as sustainable materials for spin electronics and energy harvesting application — Materials computation

The structural, mechanical, electronic, magnetic, and thermoelectric properties of alkali-based half-Heusler alloys (LiCrGe, LiCrSn, and LiCrPb) are investigated using the Wien2k code. These alloys exhibit half-metallic behavior in both ferromagnetic and antiferromagnetic phases. A phase transition from a stable ferromagnetic phase to a more stable antiferromagnetic phase indicates ductility. In the antiferromagnetic phase, using GGA exchange–correlation functional with 10,000 K-points, a band gap is observed in the spin-up state, with band gap energies of 0.9367 eV, 0.7762 eV, and 0.7913 eV, respectively. The alloys have a spin magnetic moment of −3μB, consistent with the Slater–Pauling rule. They also exhibit high Curie temperatures and 100% spin polarization in the spin-down state. The alloys LiCrZ (Z = Ge, Sn, Pb) shows promising thermoelectric behavior. Using the BolzTrap package, we observed, high Seebeck coefficient, electrical conductivity, low thermal conductivity, and enhanced power factor. The p-type LiCrZ (Z = Ge, Sn, Pb) compounds show thermoelectric figure of merit of 0.52, 0.76, and 0.84 at 1200 K, while n-type compounds have figure of merit of 0.56, 0.65, and 0.80 at the same temperature. These properties make these materials promising for spintronic and thermoelectric applications.

Ab initio investigation of the structural, mechanical, electronic, thermodynamic, and optical properties of V2FeNiGe2 and Hf2FeNiSb2 double half-Heusler compounds

In the present work, using ab initio density-functional theory methods based on the Quantum ESPRESSO package, we have investigated the structural, elastic, electronic, and optical properties of 18-electron V2FeNiGe2 and Hf2FeNiSb2 double half-Heusler alloys. The calculated elastic properties suggest a ductile behavior with metallic bonding for V2FeNiGe2 and a brittle behavior with covalent bonding for Hf2FeNiSb2. The thermodynamic properties (Debye temperature, melting temperature) are also predicted and discussed for the studied alloys. The alloys are found to be semiconducting with indirect band gaps of 0.53 eV for V2FeNiGe2 and 0.47 eV for Hf2FeNiSb2. We also computed and analyzed their optical properties (dielectric function, optical conductivity, refractive index, absorption index, and reflectance) and our calculations suggest that both materials have high absorption coefficient and optical conductivity in the UV as well as visible region. The results make them potential candidates for the manufacture of opto-electronic devices.

Study of the physical properties of the half-heusler XBrH with (X= sr, Ca and mg) compounds

Half-Heusler alloys are among the most promising thermoelectric materials for medium- and high-temperature waste heat recovery applications. This study investigates the physical properties of Half-Heusler compounds XBrH, with X = Sr, Ca, and Mg. We explored the structural, electronic, optical, and thermoelectric properties of these compounds using density functional theory (DFT) as implemented in the Wien2k package. The Generalized Gradient Approximation (GGA) as proposed by Perdew-Burke-Ernzerhof (PBE) and the modified Becke-Johnson (mBJ) functional were employed to calculate the exchange-correlation interactions. After doing structural optimization for a range of parameters, we discovered that the SrBrH compound is more stable than the CaBrH and MgBrH compounds. Our results show that the density of state calculations indicate semiconductor behavior for the XBrH with (X = Sr, Ca, and Mg) compounds. We also evaluated the real and imaginary parts of the dielectric tensor, the refractive index, the absorption coefficient, the electron energy loss, and the real and imaginary components of the optical conductivity, among other optical parameters. Additionally, we investigated the figure of merit (ZT), electronic and lattice thermal conductivity, Seebeck coefficient, and electrical conductivity. The MgBrH, CaBrH and SrBrH compounds showed p-type behavior, with positive values for the Seebeck coefficient and the greatest value of ≈180 μV/K, according to the thermoelectric data. At 1000 K, the ZT reach their highest values for CaBrH, SrBrH, and MgBrH, respectively, at 2.9, 2.8, and 0.9. The physical properties of the XBrH with (X = Sr, Ca, and Mg) compounds have been studied in detail.

High-entropy-driven half-Heusler alloys boost thermoelectric performance

High-entropy-driven half-Heusler alloys boost thermoelectric performance

Ab initio analysis of structural, electronic, magnetic, thermodynamic, and elastic properties of Half Heusler alloys ZMnAs (Z = Be, Mg) for spintronics applications

In this study, the structural, electronic, magnetic, thermodynamic, and elastic attributes of ZMnAs (Z = Be, Mg) have been investigated. These Half-Heusler alloys exhibit stability in the ferromagnetic state (FM), as demonstrated by optimization-related energy release. The half-metallicity (HM) of these compounds is examined through the band structures and density of states (DOS). In addition, the crystal field and exchange energies are reported to confirm the control of electron spin. Additionally, the double exchange process and exchange constants were premeditated. In this case, ferromagnetism (FM) is caused by the quantum exchange of electrons, as evidenced by the negative pd exchange energy and the exchange constants, rather than being a result of clustering effects. The quasi-harmonic Debye model, included within the Gibbs code, was utilized to calculate the thermodynamic properties. These two compounds are mechanically stable and show ductile nature confirmed by the value of Poisson's ratio (v), Pugh's ratio (B/G), and Cauchy pressure (CP), which demonstrates the ability to withstand substantial plastic deformation before fracturing. Based on our calculations, the half-metallic (HM) nature, thermodynamic, ferromagnetic, ductile, and high inherent magnetic moment have been evaluated. These alloys are crucial in the advancement of spintronics and renewable energy systems.

First Principles Study of Structural, Electronic, Mechanical and Density of State Properties of the Half - heusler Alloy NaCrGe

In this study, the investigated structural parameters revealed that NaCrGe is stable at beta phase. We obtained that the material is a narrow bandgap semiconductor half-Heusler alloys with measured gap of 1.050 eV. The structure NaCrGe conduction band minimum (CBM) position at gamma(Γ) and the valence band maximum (VBM) located at X-point of the Brillouin zone. This indicates that the alloy NaCrGe has indirect bandgap semiconductors. The material NaCrGe is considered hybrids between metals and semiconductors. Hence, NaCrGe is Half-metallic heusler alloy. The calculated mechanical properties indicate that NaCrGe possesses good mechanical stability, making it suitable for structural applications. B/G ratio for NaCrGe is 2.40. This implies that NaCrGe is “ductile” in nature at ambient condition. Also NaCrGe is confirmed “ductile” in nature at positive value of C11 – C44 (+48.07). PDOS shows that Na-4p, Cr-4p and Ge- 2p has the highest orbital contribution for Na, Cr and Ge atoms respectively. At fermi energy both spin up and spin down is at zero point in the plot of projected density of state (PDOS) against energy. This revealed that NaCrGe is a half metallic heusler alloy.

Enhanced thermoelectric performance of Zr1−xNiSnTax half-Heusler alloys: a first-principle study

Enhanced thermoelectric performance of Zr1−xNiSnTax half-Heusler alloys: a first-principle study