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Based on density functional theory (DFT), the structural and physical properties of NaCaZ (Z$=$N, P, As) half-Heusler (HH) semiconductor materials have been studied under pressure up to 20GPa. The ground state results show that the NaCaZ are chemically stable in $\alpha$-phase structure and exhibit semiconducting behavior with an indirect bandgap. The optical parameters like the real and imaginary components of complex dielectric function, the absorption coefficient and refractive index are investigated and discussed. The obtained results show that NaCaZ have low value of reflectivity and high absorption coefficient in low ultraviolet and visible regions and exhibit small changes under pressure. Pressure-based elastic constants and their derivative parameters show that NaCaZ are mechanically stable and have brittle nature. Above 10GPa, NaCaP and NaCaAs have ductile nature. The phonon dispersions calculations with pressure show that NaCaN and NaCaP are dynamically stable, in contrast, NaCaAs is dynamically unstable at ambient pressure. Above 10GPa, the studied compounds are dynamically stable. The mechanically, dynamically stable with low reflectivity and high absorption coefficient in the low ultraviolet and visible regions make these materials more promising as absorbers of solar cells, optoelectronic and 2D applications.

In this paper, we report the optoelectronic, thermoelectric properties and dynamic stability under the pressure of LiGaC half-Heusler within the Density Functional Theory (DFT) and semi-classical Boltzmann Transport Theory (BTT). The obtained results of the ground state show that the compound is structural, chemical, mechanical and dynamically stable in type I structure and maintains its stability under pressure. The obtained electronic properties reveal that the compound has a semiconducting nature with an indirect bandgap and the bandgap values slightly increase with pressure increase. The optical properties such as real and imaginary parts of dielectric function, refractive index and extinction coefficient, reflectivity and absorption coefficient and optical conductivity are calculated and discussed. The highest peaks of reflectivity and absorption coefficient are found in the ultra-violet (UV) region, suggesting that the compound LiGaC has a high potential for use in UV optoelectronic applications. The thermoelectric properties are also calculated in the temperature range from 300K to 900K and pressure range from 0GPa to 40GPa. At 300K and for all pressures selected, the maximum value of figure of merit is close to unity. Finally, we could make our conclusion that LiGaC is well suitable for multiple optical and thermoelectric applications.

This work aims to investigate the structural stability, magnetic and electronic properties of M₃AlC antiperovskites using density functional theory (DFT) and Monte Carlo simulation. The obtained ground state results reveal that the antiperovskites M₃AlC are stable in the ferromagnetic (FM) state with a metallic character. The calculated total magnetic moments are 5.21${\mu }_B$ and 3.34${\mu }_B$ for Mn₃AlC and Fe₃AlC, respectively, with the total moments mainly from the M atom. The ferromagnetic behavior is confirmed by computing the density of state at Fermi level and verified the Stoner criterion. The magnetic and magnetocaloric behavior of M₃AlC is investigated using Monte Carlo simulation and the obtained results demonstrate that the transition from ferromagnetic to paramagnetic state occurs at $T_C=300$K and $T_C=230$K for Mn₃AlC and Fe₃AlC, respectively. These values of $T_C$ are in good agreement with the experimental results. The magnetocaloric effect and critical behavior are studied and the obtained values of magnetic entropy change $|\mathrm{\Delta }{S}_{\mathrm{\text{mag}}}|$ at 4.5T is about 4.242J/kg.K and 3.666J/kg.K and the relative cooling power (RCP) are 342.434J/kg.K and 325.26J/kg.K for Mn₃AlC and Fe₃AlC at 4.5T, indicating that these compounds are more appropriate for magnetic refrigeration. Finally, the critical exponents ($\beta$,$\gamma$,$\delta$) are calculated and the obtained values are close to the values of mean-field model.