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 density functional theory (DFT) calculations, we report the structural, electronic, elastic, and optical properties of pure and Mg-doped LaAlO3 structure (La1- xMgxAlO3 and LaAl1- xMgxO3), respectively, with the doping concentrations of x = 0%, 20%, 40%, 60%, 80%, and 100%. Our results show that the doping of Mg along La sites introduce new band (s, p) in the valence bands that is moved towards the conduction bands with increase of doping ration (at x = 60% with a reduced bandgap of 0.04 eV), as well as indirect to direct bandgap transition along Al sites. The density of states shows that the valence band shifts towards the Fermi level by inducing a metallicity in La1-xMgxAlO3 format at 60% configuration. Elastically, LaAlO3 experiences brittle to ductile transition for both doping systems except LaAl1-xMgxO3 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.