Mg-doped LaAlO3 structure: A theoretical investigation of indirect to direct bandgap and brittle to ductile transition

Abstract

Integrating chemical dopants into a pure lattice has fueled a novel concept of tuning the physical and chemical properties of existing materials under and beyond ambient conditions. By using first-principles calculation, we report the structural, electronic, elastic, and optical properties of pure and Mg-doped LaAlO₃ structure (La_1-xMg_xAlO₃ and LaAl_1-xMg_xO₃), respectively, with the doping concentrations of x = 0%, 20%, 40%, 60%, 80%, and 100%. Our results show that Mg dopants induce metallicity along La sites at x = 60% with a reduced bandgap from 3.01 eV to 0.04 eV, as well as indirect to direct bandgap transition along Al sites at x = 40%. The density of states shows that the valence band shifts towards the Fermi level by inducing a metallicity in La_1-xMg_xAlO₃ format at 60% configuration. Mechanically, LaAlO3 experiences brittle to ductile transition for both dopingsystems except LaAl_1-x Mg_xO₃ at 40% configuration. The higher ranges of optical peaks for both systems are identified for 0‒40% ranges as compared to other configurations. Fortunately, this study reveals the tunability of LaAlO₃ structure in structural, electronic, elastic, and optical aspects and also extends the availability of this material for future optoelectronic and mechanical applications.