Salt-Inclusion Chalcogenide [Ba4Cl2][ZnGa4S10]: Rational Design of an IR Nonlinear Optical Material with Superior Comprehensive Performance Derived from AgGaS2

Searching for the coexistence of a wide energy gap (Eg > 3.5 eV) and a large second-harmonic generation efficiency (dij > 0.6 × AgGaS2) for noncentrosymmetric (NCS) materials in the IR nonlinear optical (NLO) field is highly desirable but still remains a huge challenge because of the incompatibility between them. To address this issue, a new salt-inclusion chalcogenide, namely, [Ba4Cl2][ZnGa4S10], has been designed and successfully synthesized by a chemical multisubstitution approach with chalcopyrite-type AgGaS2 (AGS) as the template. [Ba4Cl2][ZnGa4S10] adopts the NCS space group I4̅ with lattice dimensions a = b = 8.2882(4) Å, c = 15.1693(9) Å, V = 1042.04(9) Å3, and Z = 2. The structure is constructed with corner-sharing supertetrahedral [Ga4S10]8– clusters (T2) and [ZnS4]6– tetrahedra (T1) to form a three-dimensional open [ZnGa4S10]6– diamond-like framework, which is further interpenetrated with charge-balanced Ba2+ and Cl–. Remarkably, the title compound not only retains the large dij (1.1 × AGS) but also possesses a wide Eg (ca. 3.85 eV) corresponding to an ultrahigh laser-induced damage threshold (LIDT = 51 × AGS), demonstrating that it achieves the key indexes as a promising IR-NLO candidate. Furthermore, density functional theory (DFT) analysis has assisted the comprehension of the structure–property relationships. Both the experimental and DFT calculation results indicate the practicability of such a chemical multisubstitution approach to design excellent IR-NLO materials, that is, breaking the incompatibility between a wide Eg and a large dij.