First-principles calculations to investigate structural, elastic, electronic, lattice dynamic and optical properties for scandium and yttrium nitrides in zinc blend structure

We studied the structural, elastic, electronic, dynamic and optical properties of scandium and yttrium nitrides in the zinc blend structure. The GGA, LDA and GGA-PBESOL approaches, as well as the HSE hybrid functional, were used in the representation of the electronic exchange and correlation effects. The lattice constant, the bulk modulus and its pressure derivative calculated in the HSE hybrid approach are predictions. The elastic constants and B/G ratio infer that ScN and YN are elastically stable and ductile in nature. ScN and YN in the zinc blend structure show an isotropic linear compressibility and anisotropic Young's modulus, shear modulus and Poisson's ratio. The anisotropy and hardness in ScN and YN compounds are more pronounced in the LDA approach. The X–X (W–W) direct band gap in scandium (yttrium) nitride translates its semiconductor character in the zinc blend structure. The N: p orbit and small contribution of Sc: d (Y: d) site are responsible to the optical modes, while Sc: d (Y: d) site and small contribution of N: p orbit are the sign of acoustical modes. The absorption peaks are assigned to photo transitions energies from maximum valence band to minimum conduction band.