Ab Initio calculations of the structural, electronic and elastic properties of the MZN₂ (M = Be, Mg; Z = C, Si) chalcopyrite semiconductors

Four ternary semiconductors with the chalcopyrite structure (BeCN₂, BeSiN₂, MgCN₂, and MgSiN₂) were studied using the first principles methods. Their structural, electronic, optical and elastic properties were calculated. All these materials were found to be the indirect band gap semiconductors, with the calculated band gaps in the range from 3.46 eV to 3.88 eV. The degree of covalency/ionicity of the chemical bonds in these compounds was compared. Anisotropy of the optical properties of these tetragonal crystals was demonstrated by calculating the real and imaginary parts of the dielectric function ε. Anisotropy of the elastic properties of these materials was analyzed by plotting the three-dimensional surfaces of the Young moduli and their two-dimensional cross-sections. It was also shown (at least, qualitatively) that there exists a correlation between the optical and elastic anisotropy: the most optically anisotropic MgSiN₂ is also most elastically anisotropic material in the considered group. High hardness (bulk moduli up to 300 GPa) together with large band gaps may lead to new potential applications of these compounds.