Synergically Assembling Advantageous Groups toward High‐Performance Infrared Nonlinear Optical Materials A^IICdSiSe₄ (A^II = Sr, Ba)

Abstract Developing superior infrared nonlinear optical (IR NLO) materials with broad bandgap (E_g) and large NLO response is an urgent need for the highly expected mid‐/far‐IR solid‐state lasers, but challenging due to the contradiction between the critical parameters. Herein, guided by the short board effect of E_g and longboard effect of NLO response, four new IR NLO candidates A^IIB^IISiSe₄ (A^II = Sr, Ba; B^II = Cd, Hg) derived from the centrosymmetric (CS) SrIn₂Se₄, with a structural transition from Ama2 (A^IIHgSiSe₄ and SrCdSiSe₄) to Fdd2 (BaCdSiSe₄), are rationally designed and fabricated by synergically assembling advantageous structural groups. Among them, A^IICdSiSe₄ displays the optimal comprehensive performance in the known A^IIB^IIC^IVSe₄ family compounds, including a strong NLO response (≈2.1–2.7 × AgGaS₂), a wide selenide E_g (≈2.67–2.78 eV) and a high laser‐induced damage threshold (≈4.0 × AgGaS₂). Theoretical investigations uncover that the superior properties in the compounds can be contributed to the synergic‐assembly of advantageous [A^IISe₈], [CdSe₄], and [SiSe₄] units. The results enrich the chemical and structural diversities of chalcogenides, and open an avenue for the design of high‐performance IR NLO materials from the known CS compound by the aliovalent group substitution and synergically assembling strategy.