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 PnI 3 (M II =Zn, Cd; Pn=P, As), were obtained. They all exhibited defect diamond‐like structures with highly parallel‐oriented [M II PnI 3 ] 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×AgGaS 2 ), high laser‐induced damage thresholds (5.5–10.7×AgGaS 2 ), and good IR transparency. In particular, Cd 3 PI 3 and Cd 3 AsI 3 achieved phase‐matching (Δ n =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.