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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.

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.

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.

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.

Structural, elastic, and electronic properties of orthorhombic Pbnm CaTiO 3 are studied using both full potential linearized augmented plane wave (FP-LAPW) and plane-wave pseudopotential (PW-PP) methods. Exchange–correlation effects are treated by the generalized gradient approximation (GGA). The equilibrium lattice constants, the bulk modulus, its pressure derivative, and the electronic structure are in good agreement with other calculations and with experimental data. For elastic constants, Young modulus, and Poisson ratio, to our knowledge, no data are available in literature for comparison. In addition, pressure and temperature effects on the volume cell, the bulk modulus, the heat capacity, and the thermal expansion coefficient are investigated in the 0–28 GPa pressure range and in the 0–1200 K temperature range.

By employing the first-principles method of the full potential linear augmented plane waves (FPLAPW), the structural, elastic and the electronic properties of LaBi are investigated. It is found that this compound has a semiconducting small and indirect gap. Through the quasi-harmonic Debye model, in which the phononic effects are considered, we have obtained successfully the thermodynamic properties such as thermal expansion coefficient, Debye temperature and specific heats in the whole pressure range from 0 to 10 GPa and temperature range from 0 to 1600 K.