half-Heusler Alloys Research Articles

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

Effect of single and dual doping on the thermoelectric properties of FeVSb0.95Sn0.05 and Fe0.95Co0.05VSb0.90Sn0.10 half-Heusler alloys

FeVSb in addition to a set of novel FeVSb0.95Sn0.05 and Fe0.95Co0.05VSb0.90Sn0.10 half-Heusler alloys were fabricated by arc melting followed by induction melting simple methods. Impacts of single Sn-doping and double Co- and Sn-doping on the structural and thermoelectric properties of FeVSb were investigated in this article. Structural and thermoelectric properties of FeVSb, FeVSb0.95Sn0.05 and Fe0.95Co0.05VSb0.90Sn0.10 compounds have been extensively studied in this work. N-type conduction was confirmed for the FeVSb system and for the doped FeVSb0.95Sn0.05 and Fe0.95Co0.05VSb0.90Sn0.10 alloys. The absolute value of Seebeck coefficient for the single Sn-doped sample increased from 127 μV/K to 155 μV/K, with the temperature increasing. Similarly, the Seebeck coefficient of the double Co- and Sn-doped alloy also increased from 40 μV/K to 60 μV/K. The thermoelectric power factor was notably enhanced for the dual doped Fe0.95Co0.05VSb0.90Sn0.10 alloy reaching 14 μW/cm.K2. Lattice thermal conductivity of the single Sn-doped FeVSb0.95Sn0.05 alloy decreased considerably over the whole temperature range. A maximum zT of 0.084 was achieved for FeVSb0.95Sn0.05 alloy at 575 K. The improved figure of merit due to doping is attributed to the phonon scattering at point defects. Sn-doping has significantly reduced thermal conductivity due to the enhanced point-defect and electron–phonon scatterings which contributed to improved thermoelectric figure of merit. Our findings showed also that the room-temperature thermal conductivity is seriously reduced via Sn and Co dual doping leading to higher ZT value for Fe0.95Co0.05VSb0.90Sn0.10 alloy. Promising candidates for further thermoelectric applications could be achieved by Sn-doping and double Co- and Sn-doping.

Strain induced ductile to brittle transitions of NiNbAl half-Heusler alloy

The present work is to explore the effect of strain on NiNbAl, half-Heusler alloy. We have investigated the properties of NiNbAl half-Heusler alloy using Density Functional Theory (DFT). The isotropic strains (tensile and compressive) are applied to examine the occurrence of phase transitions in the alloy. Induction of strain alters the electronic, mechanical and thermodynamic properties of the alloy. On application of strain, the alloy undergoes transition from semimetal to direct band gap semiconductor at 4 % tensile strain and semimetal to metallic transition at −6% compressive strains. This electronic phase transitions occur due to the change in the interatomic distance between the atoms in the alloy. It is found that the energy band gap value increases up to 12 % tensile strain and starts decreasing for the further increase in tensile strain. The mechanical properties of the alloy under strains are analysed and their variation under compressive and tensile strains are compared. The alloy undergoes ductile to brittle transitions on increasing the strain beyond 4 %. The phonon dispersion curves for different strains indicate that the alloy is thermodynamically stable under strain. The present results emphasis the effect of strain on electrons, phonons and the mechanical stability of the alloy which will pave way for designing flexible semiconducting devices with suitable device functionalities.

Electronic and thermoelectric behaviour of XCaB (X = Li, Na, K) half-Heusler alloys under strain

Impact of isotropic strain (≤±10 %) on electronic and thermoelectric properties of XCaB (X = Li, Na, K) half-Heusler alloys is studied using DFT method. LiCaB possesses the maximum structural, dynamical and mechanical stability among the considered alloys. The alloys remain ferromagnetic and most of them also retain half-metallicity even in strained conditions. Inclusion of lattice thermal conductivity (κl) lowers the total figure of merit (ZTtot) to almost half (∼0.6 at 800K) of that of electronic figure of merit (ZTel) (∼1 at 200K). Ductility detests κl but favours ZTtot. Application of strain could tune electronic band structure and/or mechanical behaviour of LiCaB, KCaB increasing ZTtot to about 0.75, 0.67, respectively, at relatively larger compressive strains, except for a negligible change in NaCaB. Thus, required modifications in electronic and mechanical properties of XCaB alloys are beneficial for thermoelectric performance and can be achieved under appropriate strain application.

Structural, electronic, magnetic, and thermoelectric properties of half Heusler alloys ZrCo1-XFeXSb (X = 0, 0.25, 0.5, 0.75, 1): A DFT study

The structural, electronic, magnetic, and thermoelectric properties of half-Heusler alloys ZrCo1-XFeXSb (X = 0, 0.25, 0.5, 0.75, 1) are investigated using the density functional theory. It is evident that ZrCoSbis a non-magnetic semiconductor. This study investigates the influence of substituting Fe for Co on the electronic structure and magnetic characteristics of ZrCoSb. The alloys transform into half-metallic ferromagnets as Fe substitutes Co. The indirect band gap of the ZrCo1-XFeXSb alloys decreases with increasing Fe content. The phonon dispersion curve is studied to determine the structural stability. The calculated values for the elastic constant for each composition satisfy the criteria for mechanical stability. To analyse its thermoelectric properties, the semi-classical Boltzmann transport theory is used to determine the Seebeck coefficients, electrical and thermal conductivities, and power factor as a function of temperature.

Spin-polarized DFT investigations of novel KVSb half-Heusler compound for spintronic and thermodynamic applications

In this study we have investigated the robust phase stability, elasto-mechanical, thermophysical and magnetic response of KVSb half Heusler compound by implementing density functional theory (DFT) models in WIEN2k simulation package. The dynamic phase stability is computed in phase type I, II & III phase configurations by optimising their energy. It is observed that given compound is more stable in spin-polarized state of phase type-III. To explore the electronic band structure, we apply the generalised gradient approximation along with Hubbard potential U. The electronic band profile of the Heusler alloy display a half-metallic nature. Moreover, the calculated second-order elastic parameters divulge the brittle nature. To understand the thermodynamical and thermoelectric stability of the alloy at various temperature and pressures ranges Quasi-Harmonic Debye model is executed successfully. The computed value of magnetic moment (MM) found in good agreement with Slater-Pauling rule. Our findings confirms that the predicted half Heusler alloy can be used in various spintronics and thermoelectric applications.

Exploring the multifaceted properties: structural, electronic, magnetic, mechanical, thermodynamic, transport, and optical characteristics of rhodium-based half-Heusler alloys

Exploring the multifaceted properties: structural, electronic, magnetic, mechanical, thermodynamic, transport, and optical characteristics of rhodium-based half-Heusler alloys

The comparative study of structural, optoelectronic and thermoelectric properties of Li-based half-Heusler alloys via GGA and meta-GGA functionals

The present work aims to investigate the effects of meta-GGA functionals on the structural, optoelectronic and thermoelectric properties of LiXY(X=Be, Mg, Zn, Cd and Y=N, P, As, Sb, Bi) half-Heusler alloys using density functional theory (DFT) and classical Boltzmann transport theory. The obtained lattice constants of these alloys are in good agreement with the experimental values, exhibiting a slight decrease slightly with meta-GGA functionals compared with GGA-PBE. Band structure calculations demonstrate that the materials exhibit semiconductor character and provide validation for the use of meta-GGA functionals, particularly the r2SCAN and rSCAN, to predict the band gap values of LiXY more accurately. Optical and thermoelectric properties are calculated and discussed in detail. The results reveal that the meta-GGA functionals predict a significant change compared with GGA-PBE in the low energy and temperature region, while in the high energy and temperature regions, all four functionals present almost the same change trends.

A DFT study of the physical properties of novel vanadium-based half-Heusler alloys VYAl (Y = Ni,Pd, and Pt) pertinent to their optoelectronics application

We investigated three novel 18-valence electron count (VEC) vanadium-based half-Heusler alloys, VYAl (Y = Ni, Pd, and Pt), for their structural, mechanical, electronic, and optical properties using density functional theory (DFT). The computation was carried out employing Vienna Ab-initio Simulation Package (VASP) and all three alloys have exhibited structural, chemical, mechanical, and thermodynamic stability. We obtained the lattice constants of 5.520, 5.800, and 5.820 Å for VNiAl, VPdAl, and VPtAl, respectively. The elastic parameters imply a ductile and hard nature of the system and exhibit anisotropic behavior. Electronic band characterization demonstrated that all three alloys are semiconductors with direct narrow gaps at the Γ-point which is crucial for photovoltaic applications. In addition to that, the high density of the band states near the Fermi level indicates a promising candidate for thermoelectric conversion. The influence of SOC interaction in the system generates a small shift in the bands. From the optical response, we infer that the studied compounds have exceptional light absorption and reflection quality, making them suitable for optoelectronics purposes.

Growth of Carbon Nanofibers and Carbon Nanotubes by Chemical Vapour Deposition on Half-Heusler Alloys: A Computationally Driven Experimental Investigation.

The possibility of directly growing carbon nanofibers (CNFs) and carbon nanotubes (CNTs) on half-Heusler alloys by Chemical Vapour Deposition (CVD) is investigated for the first time, without using additional catalysts, since the half-Heusler alloys per se may function as catalytic substrates, according to the findings of the current study. As a carbon source, acetylene is used in the temperature range of 700-750 °C. The n-type half-Heusler compound Zr0.4Ti0.60.33Ni0.33Sn0.98Sb0.020.33 is utilized as the catalytic substrate. At first, a computational model is developed for the CVD reactor, aiming to optimize the experimental process design and setup. The experimental process conditions are simulated to investigate the reactive species concentrations within the reactor chamber and the activation of certain reactions. SEM analysis confirms the growth of CNFs with diameters ranging from 450 nm to 1 μm. Raman spectroscopy implies that the formed carbon structures resemble CNFs rather than CNTs, and that amorphous carbon also co-exists in the deposited samples. From the characterization results, it may be concluded that a short reaction time and a low acetylene flow rate lead to the formation of a uniform CNF coating on the surface of half-Heusler alloys. The purpose of depositing carbon nanostructures onto half-Heusler alloys is to improve the current transfer, generated from these thermoelectric compounds, by forming a conductive coating on their surface.

Electronic, phonon and thermoelectric properties of MnCrX (X = As, P, Sb) half Heusler alloys: a DFT study

Electronic, phonon and thermoelectric properties of MnCrX (X = As, P, Sb) half Heusler alloys: a DFT study

Study of structural and mechanical properties of the C2CaNa half-Heusler alloy using density functional theory approach

The mechanical properties of the half-Heusler alloy C2CaNa using density functional theory approach as installed in Quantum Espresso software was examined. We observed that C2CaNa will be easily compressed due to the small value of its bulk modulus. The values of the lattice constant a0, elastic constants (C11, C12, C14), Young’s modulus E, Piosson’s ratio ν, Shear modulus G, Zener anitropy A, pressure derivative B′, and band-gap Eg were obtained. Also the Voigt approximation, Reuss approximation and the Voigt–Reuss–Hill average of the approximation were gotten. Calculated values of G/B ratio is 0.581; this shows that C2CaNa has low resistance opposed to shear deformation. The B/G ratio evaluated for C2CaNa is 1.72. This implies that C2CaNa is “brittle” in nature at ambient condition. Our calculated elastic constants (C11, C12, and C44) for C2CaNa satisfied the following mechanical stability conditions for cubic structure: C11 – C12 > 0, C44 > 0, and C11 + 2C12 > 0. The value of C12 is an indication that C2CaNa is mechanically stable. This examination gives important experiences into the primary dependability and mechanical way of behavior of this material, this will empower advance material plan and application.

Iridium's influence on the structural, electronic and mechanical characteristics of ZrCo1-xIrxSb half-heusler alloys

Structural, electronic and mechanical properties ofZrCo1−xIrxSbHalf-Heusler alloys with varying x concentrations (x = 0, 0.125, 0.25, 0.375, 0.5, 0.625, 0.75, 0.875, and 1) were studied by performing the exchange-correlation (XC) energy evaluated using the local density (LDA) and generalized gradient (GGA) approximations. The calculated lattice constant, bulk modulus, and band gap energy of the ternary alloy show good agreement with previous theoretical predictions. The results indicate that an increase in Ir atom concentration in the alloy leads to an enlargement of the lattice constant (from 6.10 to 6.36 Å) and bulk modulus (from 138.09 to 149.70 GPa), resulting in increased volume and hardness of the compound. Moreover, the Engel-Vosko generalized gradient approximation (EVGGA) and modified Becke-Johnson (mBJ) schemes were employed to improve the calculations of the band structure and density of states. The studied alloys exhibit semiconductor characteristics, with a direct band gap for both x = 0.75 and x = 0.875 concentrations and an indirect band gap for the rest of the concentrations. The computed elastic constants for ZrCo1−xIrxSb alloys satisfy the requirements for mechanical stability. The VRH approximations have been used to determine the bulk modulus, shear modulus, Young's modulus, Poisson's ratio and Hardness. In addition, we also determined the anisotropy factor, sound velocities and Debye temperature.

DFT+U investigation of electronic, optical, and thermoelectric properties of YAuX (X=Si or Ge or Sn) half-Heusler alloys

Half-heusler alloys are fascinating thermoelectric materials because they have superior mechanical and transport properties. In this study, we used dft+u calculations and the Boltztrap equation to examine the electronic, optical, and thermoelectric properties of YAuSi, YAuGe, and YAuSn half-heusler alloys. The DFT+U approach predicted band gaps of 1.2767 eV, 0.611 eV, and 1.5741 eV for YAuGe, YAUSn, and YAuSi, respectively. We also observed that all materials under consideration have a broad absorption spectrum ranging from 1 eV to 12 eV, with notable peaks in the visible and UV ranges. The obtained opto-electronic properties position the three alloys as promising candidates for photovoltaic applications. Finally, thermoelectric property calculations revealed that the figure of merit values for YAuSi, YAuGe, and YAuSn HH alloys were 0.730, 0.726, and 0.736 at 800 K, respectively suggesting the materials are also suitable candidates for application in the field of thermoelectricity

Comprehensive investigation of half Heusler alloy: Unveiling structural, electronic, magnetic, mechanical, thermodynamic, and transport properties

This study employs density functional theory (DFT) using Wien2k to comprehensively analyze the essential properties of two half-Heusler alloys, KCrSi and KCrGe. Our findings demonstrate that the ferromagnetic Type 2 configuration exhibits superior stability over non-magnetic and antiferromagnetic states for all KCrZ (Z = Si, Ge) alloys. These alloys exhibit complete spin polarization and half-metallic character, with calculated magnetic moments of 3 μB for both KCrSi and KCrGe. The Curie temperature (TC) is determined using the mean field approximation. Mechanical stability is assessed through second-order elastic constants (SOECs), and electronic properties are analyzed using local spin density approximation (LSDA), Perdew-Burke Generalized Gradient Approximation (PBE-GGA), and Tran-Blaha modified Becke-Johnson (TB-mBJ) schemes, confirming the retention of the half-metallic nature. The negative enthalpy of formation (ΔH) suggests material stability. The use of semi-classical Boltzmann theory, incorporated through the sophisticated scheme of BoltzTraP, explores transport coefficients. High pressures and temperature discrepancies in thermodynamics are considered by implementing the quasi-harmonic Debye approximation to illustrate stability. Finally, optical properties are summarized to assess the applicability of this alloy for optoelectronic applications. The overall characteristics of these particular alloys suggest potential applications in sustainable thermoelectric and optoelectronic features.

A computational analysis of thermoelectric behaviour of $$d^{0}$$ half-Heusler alloys GeKCa and GeKSr

A computational analysis of thermoelectric behaviour of $$d^{0}$$ half-Heusler alloys GeKCa and GeKSr

Double half Heusler (DHH) alloys with a high absorption coefficient shed light on the optoelectronic, thermoelectric, and structural, properties of X4Fe2Hf4Pt2 (X = Bi, Sb), derived from DFT data analysis

In this investigation, we employ density functional theory (DFT) with the generalised gradient approximation of Perdew–Burke–Ernzerhof (GGA-PBE) and the modified Beck-Johnson approach (mBJ-GGA). Our focus is on examining the optoelectronic and thermoelectric properties of Bi4Fe2Hf4Pt2 and Sb4Fe2Hf4Pt2 compounds. The findings indicate that both compounds are stable in non-magnetic phase (NM). Regarding electronic characteristics, it is revealed that these compounds are direct bandgap semiconductors. The optical analysis suggests that these compounds demonstrate high reflectivity within the visible and ultraviolet spectra, rendering them promising candidates for solar cells and photovoltaic applications. Furthermore, these materials present as highly promising candidates for thermoelectric purposes due to their remarkable figure of merit (ZT) and notable Seebeck coefficient (S) values. However, there is a lack of theoretical or experimental data available for these compounds for conducting comparison with our results. We think future experimenters attempting to synthesise these chemicals experimentally will benefit from the current study.

The effect of preparation method on transport and thermoelectric properties of Hf1.75Ti0.25FeNiSb2-xInx double half-Heusler alloys

The effect of preparation method on transport and thermoelectric properties of Hf1.75Ti0.25FeNiSb2-xInx double half-Heusler alloys

Unravelling the structural, electronic, mechanical and thermoelectric properties of half-Heusler alloys NaYX (X = C, Si, Ge, Sn)

We investigate the structural, electronic, and thermoelectric properties of the newly designed half-Heusler (hH) alloys NaYX (X = C, Si, Ge, Sn) using first-principles methods combined with Boltzmann transport theory. Our results indicate that the hH alloys are chemically, mechanically, as well as dynamically stable. The electronic calculations suggest that all the alloys are direct bandgap semiconductor with a bandgap of NaYC (0.52 eV), NaYSi (0.56 eV), NaYGe (0.57 eV) and NaYSn (0.65 eV). The lattice thermal conductivities of the hH alloys are quite low (12-24 W m−1 K−1) at room temperature. The computed figure of merit (ZT) for p-type charge carrier concentration show higher value for NaYC alloy (ZT = 0.57) as compared to NaYSi (ZT = 0.07),NaYGe (ZT = 0.27) and NaYSn (ZT = 0.42) at 1200 K, respectively. Altogether, our results indicate the potential of hH alloys for the high-temperature thermoelectric applications.