Systematic studies of the structural, optoelectronic and thermoelectric characteristics of Hafnium based zintl HfCu2X2 (X= N, P, As, Sb and Bi) compounds

By using first principles calculations the structural, optoelectronic and thermal properties of HfCu2X2 (X = N, P, As, Sb, Bi) belong to Zintl family are calculated via WIEN2K code. The volume of the unit cell is optimized at ground state by including modified Becke-Johnson (mBJ) potential. HfCu2X2 Zintl phase shows metallic behavior due to overlapping in between high symmetry Γ→K and Γ→M points and missing gap behavior between conduction and valence band. In TDOS, the major participation is due to copper (Cu) followed by Hafnium (Hf) and (X) elements, while in PDOS the strong hybridization for the necessary electrical trasportation between Cu-d of valence and (Hf-d and X-p) states of conduction bands is observed for the current studies. The attributes of optical are calculated via dielectric function such as real/imaginary parts with other optical constants like refractive index, absorption etc. The maximum reflection throughout occurs in the HfCu2Bi2 compound, while HfCu2Sb2 has the highest extinction coefficient, which indicates that it absorbs more photons than the others. Further evidence that all these materials are excellent absorbers and promising new candidates for high range frequency-energy optical devices. By using BoltzTrap transport theory, thermoelectric response of the Hf-based materials is investigated and reported between temperature range from 0 to 800 K. It can be seen that HfCu2As2 compound shows higher value of ZT that is 1.1 followed by HfCu2N2 and HfCu2Bi2 with values (1 and 0.9) at 50 K temperature. Further the compound HfCu2As2 depicts (n-type) while HfCu2Bi2 shows (p-type) nature due to the presence of Seebeck curves in these negative/positive regions within 50–550 K temperature range. Materials with strong thermoelectric capabilities are generally found in high reflectivity zones and potentially effective in preventing solar heating.