First-principles calculations to investigate electronic, optical, thermodynamic and thermoelectric properties of new Na6ZnX4 (X=O, S, Se) ternary alloys

We report a first principle investigation on the new type of ternary semiconductor alloys Na6ZnX4 (X = O, S, Se). Structural and elastic properties show that these elements present low formation energy and it's mechanically stable. The obtained electronic energy band gap results show direct electronic transition along the Γ-symmetry direction involving X-s states (X = O, S, Se) in the valence band maximum and mixed contributions from Na-s and Zn-d states. Optical absorption as high as 104 cm−1 is observed in the visible region in the spectrum, with maximum absorbance being as high as 106 cm−1 in the ultraviolet region. Quasi-harmonic approximations are used to investigate the thermodynamic properties, which show the solid characteristics of the alloys even at high temperature range. Our investigation shows Na6ZnSe4 and Na6ZnO4 to be the best materials among the studied compounds for photovoltaic applications and Na6ZnS4 as the best thermoelectric candidate. The electronic band structure and the physical properties reported for the compounds are reveled for the first time. •First principle investigation on the new type of ternary semiconductor alloys Na6ZnX4 (X = O, S, Se).•Structural, elastic and electronic properties show that these elements present low formation energy and it's mechanically stable with a direct electronic transition along the Γ point.•Ternary alloys exhibit high absorption coefficient as high as 104 cm−1 in the visible range showing their interest in optoelectronic and photovoltaic applications.•Thermoelectric properties of these ternary alloys revealed an enhancement in the Seebeck coefficient and an improvement of power factor with temperature exceeding those of binary semiconductor ZnO, ZnS and ZnSe.•Na6ZnO4 is suitable to be the best material among the studied compounds for photovoltaic applications and Na6ZnS4 and Na6ZnSe4 as the best thermoelectric candidates.