KInSi1.32Sn0.68Se6: An Infrared Nonlinear Optical Material Containing Three Types of Tetrahedral Units

The deficiency of nonlinear optical (NLO) materials in the infrared region pushes continuous exploration of new ones with desired performances. In this work, a novel pentanary selenide KInSi1.32Sn0.68Se6 is discovered by using a high-temperature solid-state reaction. It crystallizes in the monoclinic noncentrosymmetric space group Cc featuring a 3D [(InSi1.32Sn0.68Se6)(-)](n) polyanionic network, and its powder sample presents promising NLO behaviors, namely 1.3-times second-harmonic generation response and close laser-induced damage threshold than those of benchmark AgGaS2 . Besides, it is phase-matchable and shows a wide transparent region. Theoretical calculation addressing its electronic structure and optical property is also performed.