Optoelectronic, thermodynamic and vibrational properties of intermetallic MgAl2Ge2: a first-principles study

Abstract

Intermetallic compounds with CaAl2Si2-type structure have been studied extensively due to their exciting set of physical properties. Among various alumo-germanides, MgAl2Ge2 is the new representative of CaAl2Si2-type structures. Our previous study explores the structural aspects, mechanical behaviors and electronic features of intermetallic MgAl2Ge2. The present work discloses the results of optoelectronic, thermodynamic and vibrational properties of MgAl2Ge2 via density functional theory-based investigations. The band structure calculations suggest that MgAl2Ge2 possesses slight electronic anisotropy and the compound is metallic. The Fermi surface topology reveals that both electron- and hole-like sheets are present in MgAl2Ge2. The electron charge density map indicates toward the dominance of covalent bonding in MgAl2Ge2. The optical parameters are found to be independent of the state of the polarization of incident electric field. The large value of the reflectivity in the visible-to-ultraviolet region up to\u2009~\u200915\xa0eV suggests that MgAl2Ge2 might be a good candidate as coating material to avoid solar heating. The thermodynamic properties have been calculated using the quasi-harmonic Debye approximation. We have found indications of lattice instability at the Brillouin zone boundary in the trigonal $$P\\overline{3}m1$$\n phase from the phonon dispersion curves. However, the compound might be stable at elevated temperature and as a function of pressure. All the theoretical findings herein have been compared with the reported results (where available). Various implications of our results have been discussed in detail.