Xin Su

Thiovanadates are promising candidates for infrared (IR) nonlinear optical (NLO) applications. Here, density functional theory calculations reveal the structure–property relationships and microscopic mechanisms of A3–nMnVS4 (A = K, Rb; M = Cu, Ag; n = 1, 2). Specifically, structural dimensionality determines the optical anisotropy (birefringence): the large birefringence of 1D K2CuVS4 (0.283 @ 1064 nm) stems from the constructive vector superposition of polarizability tensors, driven by aligned tetrahedral chains and strong Cu-3d/S-3p hybridization (stronger than that of Ag analogues). Meanwhile, the strong second-harmonic-generation (SHG) response in 2D ACu2VS4 (d24 = 12.12 pm/V for KCu2VS4) is attributed to the synergistic polarization of two inequivalent Cu sites, whose local geometric distortions optimize virtual-electron-transition channels. Alkali cations (K+/Rb+) act as electrostatic scaffolds, fine-tuning active moiety densities via cell-volume effects. This work provides clear physical guidelines for designing high-performance IR NLO materials via dimensional and anionic unit engineering.

Rare earth (RE) compounds offer an advantageous platform for developing advanced optoelectronic func-tional materials. In this work, a new Ce(III)-based selenide, Ce3MnGaSe7, was rationally designed via a polyhedral substitution strategy and synthesized through a high-temperature solid-state reaction. Ce3MnGaSe7 crystallizes in the polar space group P63. Its structure features [CeSe8] polyhedral, [MnSe6] octahedral, and [GaSe4] tetrahedral units, which are interconnected through a unique triple-connectivity pattern involving simultaneous vertex-, edge-, and face-sharing. It exhibits a strong phase-matching sec-ond-harmonic generation response (~2.0 × AgGaS2) and a high laser-induced damage threshold (~3.0 × AgGaS2), achieving a good balance for an infrared (IR) nonlinear optical (NLO) candidate. Moreover, density functional theory calculations reveal that Ce3MnGaSe7 is an indirect band gap compound, with the band gap determined by the polyhedral units. The results highlight the REIII3BIICIIIQVI7 family as an out-standing system for designing new IR NLO candidates, demonstrating that polyhedral substitution is an effective way for developing new RE functional materials.

In ultraviolet (UV) nonlinear optical (NLO) metal–organic complexes (MOCs), simultaneously achieving a strong second-harmonic generation (SHG) response and high thermal and water stability has remained a persistent bottleneck. Herein, a “polar-layer-dense-locking” strategy is utilized to synthesize a 3D cadmium-based coordination polymer, Cd(imc) (imc²⁻ = imidazole-4-carboxylate), breaking the long-standing SHG-stability trade-off. Employing the rigid, π-conjugated imc²⁻ ligand with large molecular hyperpolarizability (|β_max|) as the “nonlinear source”, this strategy constructs high-performance 2D layers via µ₂-κ²-N, O dual-bridging coordination. This architecture enforces a cooperative alignment of ligand dipoles, efficiently translating microscopic |β_max| into an amplified macroscopic SHG response. The 3D topological network is achieved via strong Cd–O coordination bonds and dense interlayer packing, imparting exceptional structural stability. Cd(imc) exhibits a giant SHG response (10.0 × KDP), ultrahigh thermal stability (up to 470 °C), and remarkable water resistance (retains crystallinity for >180 days in water at room temperature and >30 days at 100 °C), alongside a wide bandgap (4.28 eV). It also exhibits good phase-matchability, making it a practical candidate for UV frequency conversion. This “polar-layer-dense-locking” paradigm establishes a synergistic mechanism to decouple the SHG-stability constraints in UV NLO materials.

At a 2 : 1 [BO ₃ ] : [BO ₃ F] ratio, CaB ₃ O ₅ F features a 1D chain (SHG d ₂₃ =1.12 V) pm V ⁻¹ and CaB ₆ O ₉ F ₂ forms a 2D layer (Δ n = 0.101). This fills a structural gap and advances the design of DUV NLO fluorooxoborates.

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.

Synergistic integration of [SO ₃ NH ₂ ] and [C(NH ₂ ) ₃ ] via small heteroatom substitution balances properties. α-C(NH ₂ ) ₃ SO ₃ NH ₂ ( P 2 ₁ / c : 190 nm, 0.068@546 nm) and β-C(NH ₂ ) ₃ SO ₃ NH ₂ ( Iba 2: 190 nm, 1.41 × KDP, 0.074@546 nm) were successfully synthesized.

This study shows arsenates' optical anisotropy and nonlinear optical properties depend mainly on [AsO₄] group density and arrangement. High-density “Neat Arrangement” maximizes birefringence; symmetric alignments enhance second-harmonic generation.

CdF(C ₆ H ₄ NO ₂ )(H ₂ O) emerges as a UV nonliner optical material that exhibits unprecedented second harmonicgeneration (3.2×KDP) and birefringence (0.26@546 nm), achieved through the presence of π-conjudated rings and a distinctive “Warren truss structure”.