标题：Defect complexes in congruent LiNbO3 and their optical signatures
作者：Li, Yanlu; Schmidt, W. G.; Sanna, S.
作者机构：[Li, Yanlu] Shandong Univ, State Key Lab Crystal Mat, Jinan 250100, Peoples R China.; [Schmidt, W. G.; Sanna, S.] Univ Paderborn, Lehrstuhl Theoret 更多
通讯作者地址：[Sanna, S]Univ Paderborn, Lehrstuhl Theoret Phys, D-33095 Paderborn, Germany.
来源：PHYSICAL REVIEW B
摘要：The structure and stability of defect clusters in LiNbO3, as well as their influence on the linear and nonlinear optical susceptibilities, are calculated within density functional theory (DFT) using semilocal and hybrid exchange-correlation functionals. In particular, the complexes modeling the Li shortage during the crystal growth, the Li-vacancy model and the Nb-vacancy model, are examined in detail. It is found that clustering significantly decreases the formation energies of all considered defects with respect to the dilute limit. The Li-vacancy model is energetically preferred with respect to the total formation energy, while the Nb-vacancy model has the lowest formation energy per single point defect. The independent-particle approximation based on the hybrid DFT electronic structure describes the LiNbO3 optical response much better than semilocal DFT. A further improvement between the calculated optical absorption and second-harmonic generation spectra with experiment is achieved if the calculations take defect complexes into account. Nb antisite polarons give rise to optical absorption within the band gap.