Mechanical, electronic and optical properties of antifluorites semiconductors X2C (X = Mg, Be)

First-principles calculations have been performed to investigate structural, mechanical, electronic, and optical properties of antifluorites Mg2C and Be2C in the framework of the full-potential linear augmented-plane wave (FPLAPW) method. The exchange–correlation effects are treated in the local-density approximation (LDA). We have evaluated the ground-state quantities such as equilibrium volume, bulk modulus and its pressure derivative as well as the elastic constants. The results of band structure and density of states, show a wide indirect band gap. In addition, we have computed the imaginary and real parts of dielectric function in order to extract the optical properties for these compounds. The results were in favorable agreement with previous theoretical works and the existing experimental data. In order to complete the fundamental characteristics of antifluorites compounds, we have analyzed their bonding character by plotting the charge densities.