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

A M M Tanveer Karim,M A Ali,I Ara,M A Alam,S H Naqib,M A Helal

doi:10.1007/s42452-021-04214-2

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 ~ 15 eV 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 Poverline{3}m1 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

Highlights

Intermetallic compounds have been studied extensively over the last few decades due to their applications in different areas such as in optoelectronics, magnetism, spintronics and thermoelectrics
Intermetallic compounds with AM2X2-type formula, where A is the rare earth element, M refers to a metal and X is the element of the main group III, IV or V of the periodic table, belonging to the Zintl phase, crystallize mainly into the ThCr2Si2-type structure and sometimes into the CaAl2Si2-type structure
The Fermi surface topography can be derived from the electronic band structure

Summary

Introduction

Intermetallic compounds have been studied extensively over the last few decades due to their applications in different areas such as in optoelectronics, magnetism, spintronics and thermoelectrics. Some of the Zintl phase compounds are promising thermoelectric materials because of their excellent structural stability at high temperatures and low thermal conductivity [1,2,3,4,5,6]. Among the AM2X2 compounds, ThCr2Si2-type and CaCr2Si2-type structured materials have been investigated thoroughly in the field of high-Tc superconductivity [12,13,14,15,16,17], the most common being the ternary pnictides [18]. The transport properties of prototype C aAl2Si2 are controlled by both electrons and holes Since their discovery, binary and ternary phases crystallizing in this structural pattern were challenging issues because of the stability limit [20]. Results obtained from the theoretical analysis reveal the suitability of M gAl2Ge2 as a potential material for future

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Conclusion