Topology-Guided Discovery of BaIn ₂ Si ₇ P ₁₂ : A Quaternary Diamond-like Framework Phosphide with Giant Second-Harmonic Generation and High Laser-Induced Damage Threshold

Achieving both a large second-order nonlinear optical (NLO) coefficient and high laser-induced damage threshold (LIDT) is a vital but addressable challenge in advanced infrared (IR) NLO material design. Herein, we report the rational design and synthesis of the first quaternary diamond-like framework (DLF) phosphide, BaIn₂Si₇P₁₂, through a topological modification and mathematical modeling combined strategy. The compound crystallizes in the non-centrosymmetric R3 space group and inherits the structural advantages of DLFs (oriented tetrahedral units) and phosphides (inherent high LIDT), exhibiting a strong NLO response (6 × AGS, surpassing most reported DLF compounds) and a high LIDT (8.3 × AGS). Density functional theory calculations reveal that the enhanced NLO response stems from the synergistic effects of high hyperpolarizability in [SiP₄] and [InP₄] tetrahedra and their orientated arrangement within the DLF. The results demonstrate that DLF phosphides represent a promising system for developing high-performance IR NLO materials and illustrating the effectiveness of this strategy.