First-principles calculations of structural, elastic, electronic, and optical properties of CaYP (Y = Cu, Ag) Heusler alloys

Our comparative study is carried out on different structural, elastic, electronic, and optical properties of two new half-Heusler CaCuP and CaAgP compounds by using first-principles calculations based on density functional density. The generalized gradient approximation (GGA) is used for studying exchange and correlation effects. The mBJ-GGA approximation is also employed to give a better approximation of the energy bandgap for the two CaCuP and CaAgP compounds. Our two compounds are more stable in cubic structure type I structure and the lattices parameters obtained in good agreement with other available data. The two compounds are mechanically stable; the calculated elastic constants strictly obey the stability criteria with brittle behavior, isotropic, and ionic nature in cubic structure type I. The electronic properties have pointed to a semiconductor behavior for the two compounds and have shown a direct gap Γ→Γ equal to 1.785 eV for CaCuP and 1.621 eV for CaAgP with mBJ-GGA approximation. The study of optical properties with mBJ-GGA approximation as a function of photons energy for a wide range between 0 and 27 eV reveals that the two half-Heusler CaCuP and CaAgP compounds display the maximum reflectivity and absorption in the ultra violet range.