钛酸钡晶体中氧空位对光学性质的影响

Effect of Oxygen Vacancy on Optical Properties in Barium Titanate Crystals

摘要: 本文基于密度泛函理论，研究了在BaTiO₃晶体中不同电荷态(0, +1, +2)氧空位的缺陷形成能。采用杂化密度泛函修正了DFT-GGA带边问题。使用FNV方法对缺陷形成能量进行修正。给出了包含电子–声子耦合的F中心和F+中心的光谱的比较准确描述。结果表明：氧空位是浅施主能级，是该材料n型导电的主要原因。根据本文的计算结果，F心吸收峰位于2.85 eV (435 nm)，F+心吸收峰则位于2.80 eV (443 nm)。F心的发射峰位于2.83 eV (438 nm)，F+心的发射峰位于2.78 eV (446 nm)。计算结果与实验结果基本一致。结果表明，这些方法对点缺陷光谱的计算是可行的。该方法的主要优点是计算量比较低，远远低于多体微扰理论GW方法中的计算量。本文的方法在满足计算精度的条件下，解决了计算量巨大的问题。为研究点缺陷的光谱性质提供了有效途径。

Abstract: In this paper, based on density functional theory, the defect formation energies of oxygen vacancies with different charge states (0, +1, +2) in BaTiO₃ crystals were investigated. Hybrid density functional is used to solve the edge of the band problem of DFT-GGA. A finite size correction scheme (FNV) was used to correct the defect formation energy. An accurate description of the spectra of F and F+ centers involving electron-phonon coupling is given. The results show that the oxygen vacancy is a shallow donor level, which is the reason for the n-type conductivity of the material. According to our calculation results, the F core absorption peak is located at 2.85 eV (435 nm), and the F+ core absorption peak is located at 2.80 eV (443 nm). The emission peak of the F center is 2.83 eV (438 nm), and that of the F+ center is 2.78 eV (446 nm). The results are consistent with the experimental results. The results show that these methods are feasible for the calculation of point defect spectra. The main advantage of this method is that the computational cost is much lower than the GW method of multi-body perturbation theory. The method in this paper solves the problem of the huge amount of computation under the condition of satisfying the calculation accuracy. It provides an effective way to study the spectral properties of defects.