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

摘要

Four ternary semiconductors with the chalcopyrite structure (BeCN2, BeSiN2,MgCN2, and MgSiN2) were studied using the first principles methods. Thestructural, electronic, optical and elastic properties were calculated. Allthese materials were found to be the indirect band gap semiconductors, with thecalculated band gaps in the range from 3.46 eV to 3.88 eV. Comparison of thedegree of covalency/ionicity of the chemical bonds in these compounds wasperformed. Anisotropy of the optical properties of these tetragonal crystalswas demonstrated by calculating the real and imaginary parts of the dielectricfunction {\epsilon}. Anisotropy of the elastic properties of these materialswas analyzed by plotting the three-dimensional dependences of the Young moduliand their two-dimensional cross-sections. It was also shown (at least,qualitatively) that there exists a correlation between the optical and elasticanisotropy: the most optically anisotropic MgSiN2 is also most elasticallyanisotropic material in the considered group. High hardness (bulk moduli up to300 GPa) together with large band gaps may lead to new potential applicationsof these compounds.