Dr. Yanlu Li, Associate Professor, State Key Lab of Crystal Materials, Shandong University, Jinan, China

Biography: Dr. Yanlu Li is currently an associate professor at State Key Lab of Crystal Materials in Shandong University, China. She received her PhD degree in Materials Physics and Chemistry from Shandong University in 2011. After that, she did her postdoctoral research on the point defects of LiNbO3 with Prof. Wolf Gero Schmidt in Paderborn University, Germany from 2012 to 2014. Until now, she has published over 40 peer-reviewed papers. Her research interest includes the first-principle studies on the point defects, doping, electronic structures, linear and nonlinear optical properties of functional crystal materials.

Speech Title: Point defects and defect-induced optical response in ternary LiInSe2 crystals: First-principles insight
Abstract: Many experiments on LiInSe2, a technologically important nonlinear optical crystal, suggest that nonstoichiometric defects play an important role in changing the crystal color and their optical applications in infrared and/or near visible regions. The exact defect species and structures remain unverified by either experiment or theory however. Thereby density functional theory within (semi)local and hybrid exchange-correlation functional is employed to determine the dominant intrinsic point defects in LiInSe2 under various environments. It is found that the isolated point defects In antisite InLi2+ and Li vacancy VLi- are dominant if Li-deficiency, while Li interstitial Lii+ turns to be energetically preferable in a Li-sufficient condition. Interstitial Ini3+ is regarded as an intermediate state to form InLi2+ (Ini3++VLi-→InLi2+) if Li-deficiency. In all possible charge-compensated defect complexes as well as Frenkel and Schottky defects, InLi2++2VLi- is the only possible complex configuration under Li-deficiency according to the defect structures and formation energies. In particular, the clustering effect decreases the formation energies of all considered defects with respect to the dilute limit. The investigation of optical response gives further evidence that the intrinsic point defects are responsible for the crystal color change and optical absorption cutoff shift, and conversely, these phenomena could be helpful for recognizing the dominant defects in LiInSe2 crystals.
Keywords: LiInSe2; Defect; Density functional theory.