The Structural Stabilities and Electronic Properties of Orthorhombic and Rhombohedral LaCrO_3 - A First-principles Study

摘要

The equilibrium structures of orthorhombic LaCrO_3 (O-LaCrO_3) and rhombohedral LaCrO_3 (R-LaCrO_3) crystals were investigated by using the plane-wave self consistent field (PWSCF) method based on density functional theory (DFT). The optimized lattice parameters for both phases are in accordance with experimental results reported in literature, confirming the reliability of LSDA+U scheme used in the calculations. We have quantificationally investigated the binding energies and electronic properties of these two types of LaCrO_3 crystals. The negative total energy and binding energies indicate the ground state property and the good structrual stability of O-LaCrO_3 crystal, which is important for the preparation of nano materials, the synthesis of ceramic materials made of doped O-LaCrO_3 crytals, as well as their applications in high technology fields, and predict the metastable property of R-LaCrO_3 crystal. Furthermore, the band structures show that O-LaCrO_3 is a direct semiconductor with wide energy gap, while R-LaCrO_3 is an indirect semiconductor with narrow energy gap. The interaction between Cr and O atoms in O-LaCrO_3 crystal possesses the character of covalent bonding.