Noncentrosymmetric chalcohalide K2Ba3Ge3S9Cl2: A new nonlinear optical material with remarkable laser-induced damage threshold

Chalcohalides are attractive infrared (IR) nonlinear optical (NLO) materials because they can take advantages of the large second-harmonic generation (SHG) responses of chalcogenides and high laser-induced damage thresholds (LIDTs) of halides simultaneously, which are two correlated while contradictory indicators of the NLO performance. Here, a new chalcohalide, K2Ba3Ge3S9Cl2, was synthesized by a high temperature solid-state reaction, and it crystallizes in the polar noncentrosymmetric space group P6(3). The fundamental structural unit [Ge3S9](6-) rings formed by three corner-sharing [GeS4](4-) tetrahedra construct the framework, which further connects with {[KS3Cl](-6)}(infinity) chains to build up the structure with Ba and K/Ba cations occupying the cavities. It exhibits a widest band gap of 3.69 eV among all Ba-based chalcohalides, and a high LIDT around 28.8 times that of AgGaS2. It exhibits a SHG intensity around 0.34 times that of AGS. These experimental results are verified by theoretical calculations on its electronic structure and optical properties. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The newly synthesized chalcohalide K2Ba3Ge3S9Cl2 has a unique structure with a wide band gap and high laser-induced damage threshold, making it a potential excellent nonlinear optical material.