Thermodynamic phase diagram and thermoelectric properties of LiMgZ (Z = P, As, Bi): ab initio method study

ABSTRACT

Using first principle calculations based on the density functional theory (DFT), the structural, elastic, electronic, and thermoelectric properties, and thermodynamic stability of the LiMgZ (Z = P, As, Bi) half-Heusler ternary compounds were studied. The results of structural calculations and elastic constants and investigation of the thermodynamic phase diagram represent stability for these compounds in the half-Heusler cubic structure with F4-3 m symmetry. Studying the electronic structure using generalised gradient approximation (GGA) as well as spin-orbit calculations (SOC) reveal that all three LiMgZ (Z = P, As, Bi) structures are non-magnetic semiconductors with an indirect band gap along Г-X direction with values of 1.63, 1.37 and 0.5 eV, respectively. The electron transport behaviours of these materials at various temperatures show that their dimensionless figure of merit (ZT) at the temperature of 200 K reaches its maximum value of 0.813, 0.81 and 0.78 for LiMgP, LiMgAs and LiMgBi, respectively.

KEYWORDS:

• DFT
• LiMgZ (Z = P, As, Bi)
• spin-orbit
• thermoelectric
• phonon

Acknowledgment

This work is the result of the research project in the Kermanshah Branch, Islamic Azad University, Kermanshah, Iran. The authors alone are responsible for the content and writing of the paper.

Disclosure statement

No potential conflict of interest was reported by the author(s).