Structural, bonding, and electronic properties of the hexagonal ferroelectric and paraelectric phases of LuMnO3 compound: a density functional theory study

We have investigated the structural, bonding, and electronic properties of both ferroelectric (FE) and paraelectric (PE) phases of the hexagonal LuMnO3 compound using calculations based on density functional theory. The structural properties have been determined by employing the generalized gradient approximation with Perdew-Burke-Ernzerhof and Wu-Cohen parameterization. The bonding and electronic properties have been treated by recently developed modified Becke-Johnson exchange potential, which succeeded to open a band gap for both PE and FE phases, in agreement with experimental predictions. The Bader's topological analysis of electronic density showed that the character of the Lu-O axial bonds changes when the crystal exhibits the PE → FE structural transition. This fact is in agreement with experimental findings. The covalent character of the Lu-O bond significantly increases due to orbital hybridization between the Lu 5dz(2) and O 2pz-states. This bonding mechanism causes the ferroelectricity in the hexagonal LuMnO3 compound.