Investigation of the Structural, Elastic, Electronic, and Optical Properties of Half-Heusler CaMgZ (Z = C, Si, Ge, Sn, Pb) Compounds

The structural, elastic, electronic, and optical properties of half-Heusler CaMgZ (Z = C, Si, Ge, Sn, Pb) compounds are investigated herein. Density functional theory based on the full-potential linearized augmented plane wave method integrated in WIEN2K is used. The PBE generalized gradient approximation (PBE-GGA) is employed for the calculation of various parameters describing the structural and elastic properties. The results of lattice parameters are comparable to other data in the literature. On the other hand, the elastic constants reveal that our five compounds meet the stability criteria. CaMgC has a ductile nature, while CaMgSi, CaMgGe, CaMgSn, and CaMgPb have a brittle nature in the cubic structure type I phase. The modified Becke–Johnson potential proposed by Tran and Blaha (TB-mBJ) is applied to improve the calculations of electronic properties. Our calculations show that the materials have semiconductor behavior, with an indirect bandgap for CaMgC, CaMgSi, CaMgGe, and CaMgSn and a direct bandgap for CaMgPb. The optical investigations reveal strong absorption in the ultraviolet range.