The Electronic, Optical and Lattice Dynamical Properties of YIr2X2 (X=Si, Ge) Polymorphs: A DFT Study

The electronic, optical, and lattice-dynamical properties of YIr 2 X 2 (X=Si, Ge) compounds are investigated using the first-principles plane-wave pseudopotential method within the GGA approximation. In particular, the lattice constant, density of state, dielectric constant, refractive index and phonon properties are calculated and discussed. The calculated lattice parameters are in good agreement with previous experimental and theoretical data, whereas the formation enthalpies of the compounds are -1.149 and -0.841 eV/f.u. indicating that the compounds are stable in the body-centered tetragonal structure. In addition, real and imaginary parts of the static dielectric constant are 52.26 and 72.68, respectively.