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A systematic theoretical investigation is carried out on the possible piezoelectric effect in the half-Heusler FeVX (X = P, As, Sb) compounds crystallizing in the cubic MgAgAs-type structure C1b by combining density functional theory (DFT) and perturbation theory (DFPT) based on the pseudopotential plane wave (PP-PW) method implemented in the ABINIT code. The ground-state properties such as the lattice constants, and the bulk modulus and its pressure derivative are obtained using both the local density approximation and the generalized gradient approximation for the exchange–correlation functional, and the results are compared with other studies. The results for the electronic properties reveal that all the compounds exhibit semiconducting behavior with a narrow indirect bandgap. In addition, the elastic, dielectric, and piezoelectric constants are computed using density functional perturbation theory. The title compounds are found to exhibit a good electromechanical coupling coefficient (k14). No experimental or theoretical data are available for their piezoelectric properties. Thus, the results of this study can be considered to represent theoretical predictions of the properties of new piezoelectric half-Heusler compounds that can be selected based on the values of their piezoelectric coefficient (e14), which are greater than the value of 0.16 C/m2 measured empirically for GaAs. Finally, the results presented herein shed light on the use of such piezoelectricity as a possible effect in various applications such as micromechanical actuators, sensors, and self-powered devices.

Structural, electronic, elastic, and transport properties of FeVX (X = As, P) half-Heusler (HH) compounds have been calculated using density functional theory (DFT). The generalized gradient approximation developed by Perdew–Burke–Ernzerhof (GGA-PBE) is utilized for the calculation of the structural properties and the mechanical parameters of FeVX (X = As, P), indicating that the studied compounds are mechanically stable. The Tran and Blaha-modified Becke–Johnson potential (TB-mBJ) is utilized to improve the investigation of the electronic structure and also indicates that the FeVX (X = As, P) compounds are narrow-gap semiconductors. Calculations of transport efficiency are performed using the semiclassical Boltzmann theory. The figure of merit ZT is near unity at room temperature, indicating that both compounds are good candidates for use in transport devices.

Des calculs de theorie de la fonctionnelle de la densite (DFT) ont ete effectues pour obtenir des geometries optimisees, les energies orbitales moleculaires occupees les plus basses (HOMO), les ene...

The structural, electronic, elastic and magnetic properties of CoCrScIn were investigated using first principle calculations with applying the full-potential linearized augmented plane waves (FP-LAPW) method, based totally on the density functional theory (DFT). After evaluating the results, the calculated structural parameters reveal that CoCrScIn compound is stable in its ferrimagnetic configuration of the type-III structure. The mechanical properties show its brittle and stiffer behavior. The formation energy value showed that CoCrScIn can be experimentally synthesized. Additionally, the obtained band structures and density of states (DOS) reflect the half-metallic behavior of CoCrScIn, with an indirect bandgap of 0.43[Formula: see text]eV. The total magnetic moment of 3[Formula: see text][Formula: see text] and half-metallic ferrimagnetic state are maintained in the range 5.73–6,79 Å. The magnetic moment especially issues from the Cr-[Formula: see text] and Co-[Formula: see text] spin-polarizations. Furthermore, the calculations of Curie temperature reveal that CoCrScIn has high magnetic transition temperature of 836.7[Formula: see text]K.

First-principles calculations, based on the density functional theory (DFT), have been used to predict the structural, elastic, electronic and magnetic properties of XMg3O4 (X = Li, Na, K and Rb) compounds. They have been performed by employing the full-potential linearized augmented plane wave method (FP-LAPW), as implemented in Wien2k code. It was found that all compounds were ferromagnetic by energy minimization procedure. The computations of elastic constants show that our compounds are mechanically stable. The electronic properties, through the density of states and band structures, indicate that these compounds exhibit half-metallic nature, and the spin up band gaps (HMgaps) were found to be5.32 (0.18) eV, 4.49 (0.28) eV, 3.01 (0.38) eV and 1.53 (0.17) eV for LiMg3O4, NaMg3O4, KMg3O4 and RbMg3O4, respectively. In addition, for all compounds, the calculated integer magnetic moment value of 1.0 µB fulfills the necessary condition of the half-metallicity. The calculated Curie temperatures $${T}_{c}$$ are 537, 365, 260 and 113 K for LiMg3O4, NaMg3O4, KMg3O4 and RbMg3O4, respectively.

The full-potential linearized augmented plane waves (FP-LAPW) method, within the density functional theory (DFT), has been used to investigate the structural and elastic properties of KRbAs, KNaAs and NaRbAs. The obtained results, utilizing the generalized gradient approximation (GGA), revealed that all compounds prefer their type-I structure ferromagnetic (FM) phase. However, only two among them, KRbAs and KNaAs, exhibit a mechanical stability thus the electronic and magnetic properties have been calculated for both compounds. In the electronic properties, we found that both compounds show a half-metallic character with direct gaps of 1.114[Formula: see text]eV and 1.514[Formula: see text]eV, in the spin-up channel, for KNaAs and KRbAs, respectively. Thus, they may be potential candidates for spin injection in the field of spintronic applications. Moreover, their integer calculated total magnetic moment of [Formula: see text] agrees with the Slater–Pauling rule.

Full-Heuslers are a group of materials that have repeatedly attracted the curiosity of scientists and researchers, especially for their use in the field of spintronics. In this work, we undertook a study on the structural, elastic, electronic, magnetic and thermodynamic properties of the full-Heusler Mn2OsGe alloy using the calculations of the first principles. Two approximations are used: the generalized approximation of the Perdew–Burke–Ernzerhof GGA–PBE gradient for electron-correlation exchange and the new modified Tran-Blaha form of the modified Becke-Johnson mBJ–GGA-PBE potential. As important results, we found that the compound Mn2OsGe is stable in the CuHg2Ti structure; on the other hand, we could also verify its mechanical stability at zero temperature and pressure. For the calculation of the electronic properties, we were able to determine the half-metallic ferrimagnetic character of our compound, which exhibits a metallic behavior in the state of the majority spins, and a semiconductor behavior in the state of the minority spins. An integer value of 2[Formula: see text][Formula: see text] has been recorded for a magnetic moment and this conforms to the Slater–Pauling rule.

The structural, electronic, elastic, and thermoelectric properties of TiIrX (X = As and Sb) half-Heusler compounds with 18 valence electrons were studied using density functional theory. The generalized gradient approximation of Perdew–Burke and Ernzerhof used for calculation of the structural parameters and elastic properties of TiIrAs and TiIrSb denotes that the computed lattice constants were in excellent agreement with the available experimental data and previous theoretical works. Furthermore, the calculated elastic constants for both compounds satisfy the Born criteria indicating their mechanical stabilities. The modified Becke–Johnson potential (TB-mBJ) was used to provide a better description of the electronic structures, which indicate that both compounds are narrow-gap semiconductors. Additionally, the investigations of thermoelectric performance were carried out using the results of ab initio band-structure calculations and the semi-classical Boltzmann theory within the constant relaxation time approximations. The predicted values of the figure of merit ZT e are close to unity at room temperature. This reveals that TiIrAs and TiIrSb compounds are excellent candidates for practical applications in the thermoelectric devices.

We have systematically investigated the structural, electronic, optical and thermoelectric properties of HfIrX (X = As, Sb and Bi) belonging to the 18 valence electron ABX family using first-principles density functional theory calculations. In the first phase, the structural parameters of HfIrX (X = As, Sb and Bi) in the cubic LiAlSi-type (F-43 m) structure such as the lattice parameters, the bulk modulus (B) and their pressure derivative $$(B^\prime )$$ are calculated using the full-potential linearized augmented plane wave method within the generalized gradient approximation GGA-PBEsol. In the second phase, investigations of electronic and optical properties were treated by the TB-mBJ exchange-correlation potentials. The third phase is devoted to the interpretation and prediction of the thermoelectric performance of our compounds by combining the results of ab initio band structure calculations and Boltzmann transport theory in conjunction with rigid band and constant relaxation time ( $$\tau )$$ approximations as incorporated in the BoltzTraP code. We note that, because of the existence of heavy elements in our compounds, spin–orbit coupling is added for both electronic and thermoelectric calculations in order to test the effect of spin–orbit interaction on these properties. Our results are compared with other theoretical and experimental data and provide guidance for practical applications in the fields of optoelectronics and thermoelectrics.

The study of the structural, mechanical, and magneto-elctronic properties of TiZrIrZ (Z = Al, Ga, In) quaternary Heusler alloys was performed using full-potential linearized augmented plane-wave (FP-LAPW) method, based on the density functional theory (DFT) with generalized gradient approximation (GGA). The findings show that the ferromagnetic phase of Type I atomic arrangement is energetically favorable. The calculated spin-polarized band structures of TiZrIrZ (Z = Al, Ga, and In) reveal that they are half-metallic materials, with indirect band gaps (half-metallic gaps) of 1.01(0.41 eV), 0.96(0.37 eV), and 0.91 (0.43 eV) in the minority spin channel, respectively. The ferromagnetism of TiZrIrZ alloys is caused by the d-orbitals of Ti and Zr atoms and the total magnetic moments verify the Slater–Pauling rule: $$M_{t} = Z_{t} - 18$$. The calculated Curie temperatures of TiZrIrZ (Z = Al, Ga, and In) are 545 K, 566 K, and 574 K, respectively. Moreover, the half-metallicity of all these alloys is kept by the volumetric strain and tetragonal deformation in the relatively large ranges, for the lattice parameter and c/a ratio, respectively.

We use the first-principles-based density functional theory with full potential linearized augmented plane wave method to investigate the structural, elastic, electronic, and thermoelectric properties of ZrIrAs, ZrIrBi, and ZrIrSb. The calculated structural and elastic constants with generalized gradient potential developed by Perdew---Burke---Ernzerhof (GGA-PBEsol) reveal that our compounds are stable in the cubic LiAlSi-type structure. The electronic structures are calculated with GGA-PBEsol and improved by Tran---Blaha modified Becke---Johnson (TB-mBJ) potential. The thermoelectric properties were determined at temperatures of 300, 600, and 800 K with respect to the p-type and n-type doping levels. We find that the thermopower factors are larger for p-type doping, implying that the hole doping provides more enhancement of thermoelectric performances in ZrIrAs, ZrIrBi, and ZrIrSb. Among them, the best thermopower values were found for the ZrIrAs compound with optimal doping levels of 46.17, 133.05, and 185.92 $$\times 1014\,\upmu \hbox {W}\, \mathrm{cm}^{-1}\; \hbox {K}^{-2}\;\hbox {s}^{-1}$$?1014μWcm-1K-2s-1 at temperatures of 300, 600, and 800 K, respectively.

We have investigated the structural properties of seven different structure types of Mg2Si which include the cubic CaF2, orthorhombic PbCl2, hexagonal Ni2In, tetragonal Al2Cu, Laves phase (cubic MgCu2), hexagonal MgZn2 and dihexagonal MgNi2 type of structures, using a full potential linearized augmented plane wave method as implemented in WIEN2k within the framework of density functional theory. The exchange–correlation potential is treated by the new form of generalized gradient approximation (GGA-PBEsol). In total energy calculations it is clearly seen that cubic CaF2-type structure is stable at ambient conditions, and it undergoes a first-order phase transition to orthorhombic PbCl2-type, then to the hexagonal Ni2In-type structure and finally to the cubic Laves phase MgCu2-type. A new structure type is predicted to be stable at high pressure. Moreover, we intend to combine the electronic structure calculations performed by mean of generalized gradient approximation and modified Becke–Johnson potential with Boltzmann transport theory as incorporated in BoltzTraP code to interpret and predict the thermoelectric performance of each stable phase as a function of the chemical potential at various temperatures. We find a high thermoelectric thermopower values in cubic CaF2-type structure that could promise an excellent candidate for potential thermoelectric applications.

In this paper, we present the study of the structural, mechanical, magneto-electronic and thermodynamic properties of the perovskite KBeO3. The calculations were performed by the full potential augmented plane wave method, implemented in the WIEN2k code which is based on density functional theory, using generalized gradient approximation. The computed formation energy and elastic constants indicate the synthesizability and mechanical stability of KBeO3. Moreover, our results showed that the latter is a half-metallic material with half-metallic gap of 0.67 eV and an integer magnetic moment of 3μB per unit cell. In addition, KBeO3 maintains the half-metallic character under the pressure up to about 97 GPa corresponding to the predicted magnetic-phase transition pressure from ferromagnetic to non-magnetic state. The volume ratio V/V0, bulk modulus, heat capacity, thermal expansion and the Debye temperature are analyzed using the quasi-harmonic Debye model.

This paper concerns a predictive investigation of the structural and elastic stability, electronic structure, and thermoelectric properties of CoVX (Ge and Si) Half-Heusler materials. The structural constants and mechanical stability are computed utilizing the (GGA-PBE) approximation. The computed lattice constants of CoVX (Ge and Si) compounds are in good accordance with other theoretical reports. Furthermore, the mechanical parameters and the related elastic constants reveal that CoVX (Ge and Si) alloys are mechanically stable and ductile. To ameliorate the computation of the energy band gap, the (TB-mBJ) method was employed. It is shown that the CoVX (Ge and Si) compounds are an indirect band-gap semiconductors. At room temperature, the computed figure of merit of CoVGe and CoVSi compounds is about unity, which denote that the CoVGe and CoVSi compounds have good thermoelectric performance and can be applied for the production of electricity in the transport devices.

We investigate the structural, electronic, magnetic and elastic properties of KMgO3, by using first principle calculations, applying the full-potential linearized augmented plane waves (FP-LAPW) method based totally on functional density theory (DFT), using Generalized Gradient Approximation (GGA) and modified Beck Johnson TB-mBJ potential in exchange correlation term. After analyzing the obtained structural parameters, the results revealed that KMgO3 compound is most stable in its ferromagnetic configuration. The formation energy value showed that this compound can be experimentally synthesized. Furthermore, the calculated band structures, and density of states (DOSs) indicate the half-metallic behavior of KMgO3. We found also that the total magnetic moment is an integer value of 3μB which confirms the half-metallic character. The evaluation of Curie temperature of KMgO3 compound is determined within the mean field approximation (MFA), and equals 560.4 K. The magnetic moment mainly originates from the spin-polarization of p electrons of O atoms.

This study reports on the structural, mechanical and magneto-electronic properties for new perovskite compound LiBeO3. In this paper, the Full Potential Linearized Augmented Plane Wave method is used to investigate these properties. The structural optimization reveals that its ferromagnetic state is more stable than those of the non-magnetic and anti-ferromagnetic phases. The calculated elastic constants and formation energy indicate that LiBeO3 is mechanically stable and experimentally synthesizable, respectively. Around the Fermi energy, the main contribution to the total DOS is due to O-p states. The studied compound is ferromagnetic half-metal with a large band gap of 7.73 eV in the spin-up channel, originated mainly by an energetic downshift of O-p orbital in this spin-direction. The calculated total magnetic moment is an integer value of 3 μB, which confirms the half-metallic character of LiBeO3. It is also characterized by a Curie temperature of 823 K, computed using mean field theory. Moreover, the half-metallicity is maintained under the pressure up to a value of 24.7 GPa. To the best of our knowledge, LiBeO3 is the first investigated half-metallic perovskite without a transition metal.

The structural, mechanical, electronic, and transport properties of RuVX (As, P, and Sb) Half-Heusler compounds are studied. The density functional theory (DFT) based on full-potential linearized augmented plane wave FP-LAPW method as integrated in the Wien2k code was used. The structural properties and mechanical parameters are carried out by mean of the generalized gradient approximation (GGA-PBEsol). The computed lattice parameters are in good accordance with the experimental data and other theoretical reports. In Addition, the elastic constants and the related elastic moduli indicate that RuVX (As, P, and Sb) compounds are ductile and mechanically stable in the cubic phase. The modified Becke–Johnson potential (TB-mBJ) was applied to enhance the calculation of the electronic properties. It is found that the RuVX (As, P, and Sb) compounds are semiconductors with an indirect band-gap. GGA + U calculations are performed to investigate the relationship between band gap and Hubbard potential. Studies of thermoelectric properties were performed by the Boltzmann transport equations as incorporated in BoltzTraP code. At room temperature, the obtained values of the figure of merit (ZT) for RuVAs, RuVP, and RuVSb compounds are around unity, which confirm that all compounds have good transport efficiency and can be utilized for electricity production and thermoelectric devices.