The Oreticalstudy On Structures And Properties Of Complex Oxides(La_1-xB_x)GaO₃Crystals

The crystal structures, electronic properties, Mulliken population and elastic propertiesof orthorhombic LaGaO3(O-LaGaO3) and rhombohedral LaGaO3(R-LaGaO3) werecalculated and analyzed by using the first-principles method based on density functionaltheory (DFT), and the local density approximation (LDA) with CA-PZexchange-correlation potential and ultra-soft pseudopotential were applied. The structuresand properties of (La7/8Nd1/8)GaO3,(La3/4Nd1/4)GaO3and (La7/8Sr1/8)GaO3were studied byusing the generalized gradient approximation (GGA) with PBESOL exchange-correlationpotential and on the fly pseudopotential. It is great importance for the development andapplications of new type materials of doped LaGaO3.The optimal lattice parameters of both crystals are in good agreement with theexperimental results, which confirms the reliability of our calculation schemes. Thecalculation results of band structures exhibit that both orthorhombic and rhombohedralphases of LaGaO3are indirect band gap semiconductors. The corresponding band gaps are3.670eV for O-LaGaO3and3.803eV for R-LaGaO3, respectively. The lower DOS value atFermi level and the calculated Mulliken population congruously indicate that O-LaGaO3ismore stable than R-LaGaO3. The results of PDOS and Mulliken population show that bothO-and R-LaGaO3are complex type crystals of covalent and ionic bonds. The ductility ofO-LaGaO3is better than that of R-LaGaO3, and the hardness of R-LaGaO3is larger slightly.The calculated results and analysis about (La7/8Nd1/8)GaO3and (La3/4Nd1/4)GaO3crystals indicate that the intensions of Ga-O covalent bonds and La-O ionic bonds decrease,and the stability of GaO6octahedra decreases with the increase of Nd concentration. Thecalculated results show that the symmetry of (La7/8Sr1/8)GaO3is higher than O-LaGaO3.(La7/8Sr1/8)GaO3is an indirect semiconductor with a band gap of3.569eV. For Ga-Ocovalent bonds, its averages of Mulliken population and intension decrease, and thestability of GaO6octahedra is weaker than that of O-LaGaO3.