Anionic Aliovalent Substitution from Structure Models of ZnS: Novel Defect Diamond‐like Halopnictide Infrared Nonlinear Optical Materials with Wide Band Gaps and Large SHG Effects

To design pnictide nonlinear optical materials with wide band gap and large second-harmonic generation, the heavy halogen I was introduced into pnictides through anionic aliovalent substitution with diamond-like ZnS as templates. Thus, four excellent halopnictide-based infrared nonlinear optical crystals, M^II ₃ PnI₃ (M^II =Zn, Cd; Pn=P, As), were obtained. They all exhibited defect diamond-like structures with highly parallel-oriented [M^II PnI₃ ] mixed-anionic tetrahedral groups, leading to excellent physical properties including wide band gaps (2.38-2.85 eV), large second harmonic generation responses (2.7-5.1×AgGaS₂ ), high laser-induced damage thresholds (5.5-10.7×AgGaS₂ ), and good IR transparency. In particular, Cd₃ PI₃ and Cd₃ AsI₃ achieved phase-matching (Δn=0.035 and 0.031) that their template β-ZnS could not do. Anionic aliovalent substitution provides a feasible strategy to design novel promising halopnictide IR NLO materials.