钙钛矿型氧化物BaBO3-δ (B=Fe、Co、Nb)电子结构和氧空位形成能的第一性原理研究

First-principles Study on Electronic Structures and Oxygen Vacancy Energies of Perovskite-type Oxides BaBO_(3-δ) (B=Fe、Co、Nb)

基于第一性原理的密度泛函理论,分别对钙钛矿型氧化物BaFeO3、BaCoO3和BaNbO3的电子结构和氧空位形成能进行了理论模拟,经优化后得到的晶胞参数与实验文献值吻合良好。通过比较密度泛函理论计算得到的晶格能和氧空位形成能,发现体系稳定性表现为BaCoO3<BaFeO3<BaNbO3。对于B位含有多种元素的体系,在实验研究中通过1130℃煅烧10 h的条件下得到了BaCo0.5Fe0.25Nb0.25O3-δ纯相并分析了其晶胞参数。理论研究中以BaCoO3为基构造了钙钛矿型复合氧化物BaCo0.5Fe0.25Nb0.25O3,并通过第一性原理计算优化了其结构,理论计算得到的晶胞参数0.397 nm与实验测定的0.407 nm相接近;通过分析此晶体态密度证实了它是电子导体;本文还分析和比较了晶体中两个B位原子间的氧空位形成能差异,发现钴离子附近的氧空位形成能非常小,在0.5～0.6 eV左右。

Based on the density functional theory（DFT） of first-principles,the characters of perovskite-type oxides BaFeO3,BaCoO3 and BaNbO3,such as crystal lattices,electronic structures and the formation energies of oxygen vacancies,were investigated with theoretical chemistry calculations.The equilibrium lattice constants of optimized structures agree well with the experimental literature values.According to the lattice energies and oxygen-vacancy formation energies from DFT calculations,the trend of crystal stability is BaCoO3〈BaFeO3〈BaNbO3.For the system containing many kinds of elements in position B,experimentally the pure phase material was obtained after 10 h sintering in 1130 ℃ and analyzed the equilibrium lattice constant.Theoretically based on the structure of BaCoO3 the perovskite-type structure of BaCo0.5Fe0.25Nb0.25O3 was constructed and optimized with first-principles calculations,the calculated equilibrium lattice constant 0.307 nm agree well with the experimental date 0.407 nm;by analyzing the crystal density of states（DOS） confirmed that it is electronic conductor;the formation energies of oxygen-vacancy between two position B ions were also analyzed,the calculated data indicated that the formation energies next to the Co ions are relatively low,about 0.5-0.6 eV.