First-principles Studies On Structures And Properties Of Ordered α-(Ga_1-xFe_x)₂O₃System

The crystal structures, electronic and optical properties of (Ga_1-xFe_x)₂O₃compound havebeen investigated by using first-principles methoed base on the density functional theory （DFT）.The crystal structure models of (Ga_1-xFe_x)₂O₃were built according to the experiment results oflattice parameters reported in the literature. By the scheme of GGA+U, the geometryoptimizations of these systems were completed at the first step. The total energies, electronic andoptical properties of α-Ga₂O₃、 α-Fe₂O₃、 GaFeO₃-A、 GaFeO₃-B、 α-(Ga_1/4Fe_3/4)₂O₃、α-(Ga_3/4Fe_1/4)₂O₃and GaFeO₃-C were calculated based on the optimized unit cells. The obtainedcalculation and analysis results are as follows:The geometry optimization results of lattice parameters agree with experiment values well.The antiferromagnetic （AFM） states of α-Fe₂O₃、GaFeO₃-A、 GaFeO₃-B、 GaFeO₃-C、α-(Ga_1/4Fe_3/4)₂O₃and α-(Ga_3/4Fe_1/4)₂O₃show higher stability than ferromagnetic （FM） states ofthem. GaFeO₃-A is the most stable system among GaFeO₃-A, GaFeO₃-B, and GaFeO₃-C for itslowest total energy. GaFeO₃-C belong to direct band gap semiconductor, while α-Ga₂O₃, α-Fe₂O₃,GaFeO₃-A, GaFeO₃-B, α-(Ga_3/4Fe_1/4)₂O₃and α-(Ga_1/4Fe_3/4)₂O₃belong to indirect band gapsemiconductor. The curve of absorption coefficient, optical conductivity, complex dielectricfunction of α-Ga₂O₃, α-Fe₂O₃, GaFeO₃-A and GaFeO₃-B on the plane of （100）,（010） and （001）are almost identical while the perovskite GaFeO₃show different anisotropy. There is noabsorption of α-Ga₂O₃system in the visible range, but the perfect compound would be atransparent crystal. The crystal of α-Fe₂O₃、GaFeO₃-A、GaFeO₃-B and GaFeO₃-C light could beabsorbed in the visible range, and a certain amount of electron-hole pairs will be generated. Theabsorption ranges of these crystals are different with each other in the visible range, and therange increasing Fe doping contentration in crystal, and the perovskite posses larger absorptionrange than corundum GaFeO₃. The real part（σ1） of the photo-conductive on the five crystals are arranged from maximum to minimum as follows: α-Ga₂O₃, GaFeO₃-C, GaFeO₃-A, GaFeO₃-Band α-Fe₂O₃.The analysis results are shown that the Fe doping concentration is able to adjust the opticalproperties of (Ga_1-xFe_x)₂O₃series crystal, and it is an important reference to experimental studyfor reference.