Effect of cations on the structural, optoelectronic, and thermoelectric properties of AMg2N2 (A = Yb, Sm, Eu) Zintl compounds; An ab-initio study

Zintl phases are prominent for their attribution to optical and thermoelectric meeds. AMg(2)N(2) (A = Yb, Sm, Eu) compounds of the zintl family were investigated through first-principles studies for structural, electronic, optical, and thermoelectric properties. Potential functionals; PBE-GGA, TB-mBJ, and Hybrid (YS-PBE0) were used to study these compounds. The behavior of all compounds YbMg2N2, SmMg2N2, and EuMg2N2 was semiconducting with band gaps 3.75 eV, 2.22 eV, and 2.67 eV respectively through YS-PBE0. The density of states (DOS) study reveals that the leading role was offered by A-d orbitals to construct conduction bands and by A-f orbitals to form valence bands. The optical nature of these materials was studied from the optical parameters like; dielectric function epsilon(omega), refractive index n(omega), energy loss function L(omega), absorption coefficient alpha(omega), extension coefficient k(omega), reflectivity R(omega), and optical conductivity sigma(omega). From this study, it is revealed that these samples are active in the visible and ultra-violet (UV) regions, due to which these materials are supposed to be suitable candidates for optoelectronic applications. Furthermore, the thermoelectric character of the titled compounds was scrutinized through the BoltzTraP2 code. The thermoelectric efficiency in the form of thermoelectric figure of merit(ZT) of AMg(2)N(2) (A = Yb, Sm, Eu) compounds are achieved 1.17, 0.64, and 0.43 respectively at somehow high temperature 950 K. From ZT and optimized level of carriers' concentrations, these materials are considered to be efficient thermoelectric.