First-Principles Calculations on Electronic,Chemical Bonding and Optical Properties of Cubic Hf_3N_4

Electronic,chemical bonding and optical properties of cubic Hf 3N4(c-Hf3N4) are calculated using the firstprinciples based on the density functional theory(DFT).The optimized lattice parameter is in good agreement with the available experimental and calculational values.Band structure shows that c-Hf3N4 has direct band gap.Densities of states(DOS) and charge densities indicate that the bonding between Hf and N is ionic.The optical properties including complex dielectric function,refractive index,extinction coefficient,absorption coefficient,and reflectivity are predicted.From the theory of crystal-field and molecular-orbital bonding,the optical transitions of c-Hf3N4 affected by the electronic structure and molecular orbital are studied.It is found that the absorptive transitions of c-Hf3N4 compound are predominantly composed of the transitions from NT22p valence bands to HfT2(dxy,dxz,dyz) conduction bands.