Investigation of structural, electrical, dynamical, optical, and thermoelectric properties of Sr-doped Mg₂Si systems using first-principles calculations

This research article explores the comprehensive characterization of Mg₈Si₄ and Sr₂Mg₆Si₈ systems, delving into their structural, electrical, dynamical, optical, and thermoelectric properties. Employing GGA and HSE06 hybrid functional calculations alongside semiclassical Boltzmann technique calculations, the study reveals intriguing insights. Through examination of cohesive and formation energies, it is established that Sr₂Mg₆Si₈ exhibits the most stable condition. Phonon dispersion confirms the structural stability of both compounds. Mg8Si4 possesses an indirect band gap of 0.222 eV, whereas Sr₂Mg₆Si₈ showcases a direct band gap of 0.752 eV under HSE06 analysis. Notably, Sr2Mg6Si8 displays superior electrical conductivity and Seebeck coefficient despite low lattice thermal conductivity, resulting in a promising thermoelectric figure of merit (ZT) of 0.64 at 700 K. Moreover, the composition Sr2Mg6Si4 exhibits a notable Power Factor of 4 × 10¹² WK⁻² m⁻¹ s⁻¹ at 700 K, highlighting its potential for thermoelectric applications.