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

Abstract Intermetallic compounds with CaAl 2 Si 2 -type structure have been studied extensively due to their exciting set of physical properties. Among various alumo-germanides, MgAl 2 Ge 2 is the new representative of CaAl 2 Si 2 -type structures. Our previous study explores the structural aspects, mechanical behaviors and electronic features of intermetallic MgAl 2 Ge 2 . The present work discloses the results of optoelectronic, thermodynamic and vibrational properties of MgAl 2 Ge 2 via density functional theory-based investigations. The band structure calculations suggest that MgAl 2 Ge 2 possesses slight electronic anisotropy and the compound is metallic. The Fermi surface topology reveals that both electron- and hole-like sheets are present in MgAl 2 Ge 2 . The electron charge density map indicates toward the dominance of covalent bonding in MgAl 2 Ge 2 . 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 ~ 15 eV suggests that MgAl 2 Ge 2 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 $$P\overline{3}m1$$ P 3 ¯ m 1 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. Graphic abstract