First-principle calculations on the structural, electronic, optical, elastic and thermal properties of the chalcopyrite $\rm{MgXAs_{2} (X = Si, Ge)}$ have been performed within the density functional theory (DFT) using the full potential linearized augmented plane wave (FP-LAPW) method. The obtained equilibrium structural parameters are in good agreement with the available experimental data and theoretical results. The calculated band structures reveal a direct energy band gap for the interested compounds. The predicted band gaps using the modified Becke–Johnson(mBJ) exchange approximation are in fairly good agreement with the experimental data. The optical constants such as the dielectric function, refractive index, and the extinction coefficient are calculated and analysed. The independent elastic parameters namely, $C_{11}, C_{12}, C_{13}, C_{33}, C_{44}$ and $C_{66}$ are evaluated. The effects of temperature and pressure on some macroscopic properties of $\rm{MgSiAs_{2}}$ and $\rm{MgGeAs_{2}}$ are predicted using the quasiharmonic Debye model in which the lattice vibrations are taken into account.

In this paper, we present the results of a detailed computational study of the structural, electronic, optical, magnetic and thermoelectric properties of the CsNiO$_2$ and CsCuO$_2$ Heusler alloys, by using the full potential-linearised augmented plane wave (FP-LAPW) method. The calculated structural parameters of the title compounds are in excellent agreement with the available theoretical data. The equilibrium ground-state properties were calculated and it was showed that the studied compounds are energetically stable in the AlCu$_2$Mn phase within the ferromagnetic state. In order to evaluate the stability of our compounds, the cohesion energies and formation energies have been evaluated. The optoelectronic and magnetic properties revealed that these compounds exhibit half-metallic ferromagnetic behaviour with large semiconductor and half-metallic gaps. This behaviour is confirmed by the integer values of total magnetic moments, but these compounds do not satisfy the Slater–Pauling rule. Furthermore, the thermoelectric parameters are computed in a large temperature range of 300–800 K to explore the potential of these compounds for high-performance technological applications.

In this work, first-principles calculations were utilised to study the structural, magnetic and electronic properties of Mn$_2$PtZ (Z = V, Co) based on density functional theory (DFT). These compounds are predicted to be more stable in the Cu$_2$MnAl structure and the FM ground state is energetically favourable, withmagnetic moments of 4.93 and 9.04 $μ$$_B$/f.u. for Mn$_2$PtV and Mn$_2$PtCo compounds, respectively. Additionally, the computed total magnetic moments of both compounds agree well with the Slater–Pauling rule, MT = NV−24, andthe main contribution in these magnetic moments emanates from Mn atoms for both materials. Through the results on the spin-polarised electronic properties (band structures and densities of states), it is found that both alloys reveala complete half-metallic (HM) character with a half-metallic gap using GGA+U+TB-mBJ approximation.