Interrelationship of bonding strength with structural stability of ternary oxide phases of MgSnO3: A first-principles study

Abstract

We have studied the Ilmenite, Perovskite and LiNbO3 type crystal structures of ternary oxide MgSnO3 by first-principles methods using density functional theory (DFT) and beyond. We conclude that MgSnO3 in LiNbO3 type is both mechanically and dynamically stable, whereas Ilmenite and Perovskite crystal structures are mechanically stable but dynamically unstable. Vibrational stability in MgSnO3 warrants some distortion in the octahedra caused due to the strength of bonding between the atom pairs Sn–O in LiNbO3 type crystal structure. Similarly, Ilmenite and Perovskite crystal structures require a higher number of Mg–Sn and (Mg–Mg, Sn–Sn, O–O and Mg–O) bonds respectively. Ilmenite and LiNbO3 type crystal structures can be used as window layers featuring a large bandgap of 5.22 eV and 3.88 eV respectively, along with a lower absorption coefficient and reflectivity. Likewise, Perovskite crystal structure with a bandgap of 2.55 eV can be deployed as an absorber layer that traps green light of the solar irradiation in tandem solar cells. Perovskite crystal structure has the lowest charge carrier effective masses among all the structures in MgSnO3. LiNbO3 type crystal structure shows a high hardness of 56.5 GPa. It should be tested experimentally in applications requiring super-hard materials.