Confirming the structural stability and reaching the depth of quaternary Heusler alloys LiMgAgZ (Z = Al, Ga) for thermoelectric device applications: A first-principles study

Abstract

First principles calculations including structural, electronic, elastic, vibrational, thermodynamic and thermoelectric properties of novel quaternary Heusler compounds LiMgAgZ (Z = Al, Ga) have been studied for the first time using density functional theory (DFT). The quaternary Heusler structured LiMgAgAl and LiMgAgGa alloys possess a face centered cubic structure and belong to the space group F-43m (group No. 216). The band structure calculations reveal that these compounds are metallic. Further, the Fermi surface studies have demonstrated their metallic behavior. The mechanical stability is predicted based on calculated elastic constants, Poisson’s ratio as well as other mechanical parameters. The thermoelectric nature of these compounds is studied utilizing BoltzTrap code. The phonon dispersion curves of LiMgAgZ (Z = Al, Ga) are in the high symmetry directions over the Brillouin zone which indicate the vibrational stability of these compounds. The phonon modes are observed to be Raman active or Infrared active based on the representation of Eigenvectors. The stability of the compounds is also analyzed for their thermodynamic applications. The calculated results reveal unique surface topologies and thermoelectric responses for the compounds under investigation. This work is carried out to inspire researchers to synthesize such types of compounds and analyze their potential for the development of modern thermoelectric devices.