Novel ternary Zintl phosphide halides Ba3P5X (X = Cl, Br) with 1D helical phosphorus chains: synthesis, crystal and electronic structure

Black single crystals of two novel ternary phosphide halides, Ba3P5Cl and Ba3P5Br, were grown using molten metal Pb-flux high-temperature reactions. These compounds were structurally characterized with the aid of the single-crystal X-ray diffraction (SCXRD) method at 100(2) K. The SCXRD shows that both compounds are isostructural and adopt a new structure type (space group R3̄c, No. 167, Z = 6) with unit cell parameters a = 14.9481(16) Å, c = 7.3954(11) Å and a = 15.045(4) Å, c = 7.537(3) Å for Ba3P5Cl and Ba3P5Br, respectively. Cl- and Br- anions are octahedrally coordinated by Ba2+ cations, thus composing a face-sharing 1D infinite chain 1∞[XBa3]5+ running along the [001] direction. Moreover, the crystal structures feature peculiar one-dimensional disordered infinite helical chains of 1∞P-, composed of partially occupied phosphorous atoms, each being a superposition of three symmetrical copies of the ordered phosphorus chain, with continuity along the c-axis. Ba3P5X (X = Cl, Br) compounds are charge-balanced heteroanionic Zintl phases according to the charge-partitioning scheme (Ba2+)3[P-]5X-. The presumed semiconducting behavior of both compounds corroborates well with the results of the electronic structure calculations performed with the aid of the TB-LMTO-ASA code.

Rare-earth-based chalcogenides and their derivatives: an encouraging IR nonlinear optical material candidate

With the continuous development of laser technology and the increasing demand for lasers of different frequencies in the infrared (IR) spectrum, research on infrared nonlinear optical (NLO) crystals has garnered growing attention. Currently, the three main commercially available types of borate materials each have their drawbacks, which limit their applications in various areas. Rare-earth (RE)-based chalcogenide compounds, characterized by the unique f-electron configuration, strong positive charges, and high coordination numbers of RE cations, often exhibit distinctive optical responses. In the field of IR-NLO crystals, they have a research history spanning several decades, with increasing interest. However, there is currently no comprehensive review summarizing and analyzing these promising compounds. In this review, we categorize 85 representative examples out of more than 400 non-centrosymmetric (NCS) compounds into four classes based on the connection of different asymmetric building motifs: (1) RE-based chalcogenides containing tetrahedral motifs; (2) RE-based chalcogenides containing lone-pair-electron motifs; (3) RE-based chalcogenides containing [BS3] and [P2Q6] motifs; and (4) RE-based chalcohalides and oxychalcogenides. We provide detailed discussions on their synthesis methods, structures, optical properties, and structure-performance relationships. Finally, we present several favorable suggestions to further explore RE-based chalcogenide compounds. These suggestions aim to approach these compounds from a new perspective in the field of structural chemistry and potentially uncover hidden treasures within the extensive accumulation of previous research.

Ba10In2Mn11Si3O12S18: First Hexanary Oxychalcogenide Containing an Infrequent Three-Dimensional Noncentrosysmmetric Framework

Noncentrosymmetric (NCS) oxychalcogenides have attracted great attention in recent years due to their immense potential as candidates for IR nonlinear-optical (NLO) applications. Despite notable advancements in this field, the discovery of oxychalcogenides with three-dimensional (3D) framework structures remains a formidable challenge. In this study, we report the discovery of the first hexanary oxychalcogenide, Ba10In2Mn11Si3O12S18, exhibiting second-order NLO activity, using a high-temperature solid-phase method. This compound showcases a novel structure type, featuring an uncommon NCS 3D [In2Mn11Si3O12S18]20- framework formed by vertex-sharing [(Mn/In)S6] octahedra, [(Mn/In)OS3] tetrahedra, and [SiO4] tetrahedra, with charge-balanced Ba2+ cations occupying the channels. Our study serves as a source of inspiration for researchers to further investigate the synthesis of novel NLO-active oxychalcogenides with 3D frameworks.

Pinalites: Optical Properties and Quantum Magnetism of Heteroanionic A3MO5X2 Compounds

Heteroanionic compounds, which contain two or more types of anions, have emerged as a promising class of materials with diverse properties and functionalities. In this paper, I review the experimental findings on Ca3ReO5Cl2 and related compounds that exhibit remarkable pleochroism and novel quantum magnetism. I discuss how the heteroanionic coordination affects the optical and magnetic properties by modulating the d-orbital states of the transition metal ions. Subsequently, I compare these materials with other heteroanionic and monoanionic compounds and highlight the potential of A3MO5X2 materials for future exploration of materials and phenomena.

Anisotropic structure building unit involving diverse chemical bonds: a new opportunity for high-performance second-order NLO materials

We define the anisotropic structure building unit that encompasses diverse chemical bonds (ABUCB). The ABUCB is highly likely to cause anisotropy in both crystallographic structure and spatial electron distribution, ultimately resulting in enhanced macroscopic optical anisotropy. Accordingly, the (PO3F)2- or (SO3F)- tetrahedron involving the unique P-F or S-F bond serves as such an ABUCB. The distinct chemical bond effectively alters the microscopic nature of the structure building unit, such as polarizability anisotropy, hyperpolarizability, and geometry distortion; this consequently changes the macroscopic second-order nonlinear optical (2nd-NLO) properties of the materials. In this review, we summarize both typical and newly emerged compounds containing ABUCBs. These compounds encompass approximately 90 examples representing six distinct categories, including phosphates, borates, sulfates, silicates, chalcogenides and oxyhalides. Furthermore, we demonstrate that the presence of ABUCBs in DUV/UV NLO compounds contributes to an increase in birefringence and retention of a large band gap, facilitating phase matching in high-energy short-wavelength spectral ranges. On the other hand, the inclusion of ABUCBs in IR NLO compounds offers a feasible method for increasing the band gap and consequently enhancing the larger laser-induced damage threshold. This review consolidates various trial-and-error explorations and presents a novel strategy for designing 2nd-NLO compounds, potentially offering an opportunity for the development of high-performance 2nd-NLO materials.

Nonlinear optics properties of Ni-Sb2Se3 nanofilms in the near-infrared region

S b 2 S e 3 is an emerging material in recent years, and past studies have shown that it has good optoelectronic properties when doped with metals. In this paper, pure S b 2 S e 3 films and N i-S b 2 S e 3 films with different doping contents (1, 2, 3 W) were prepared by magnetron sputtering technology. The nonlinear optics properties of the sample films were investigated using femtosecond (fs) Z-scan technology under 800 nm. The results showed that both pure S b 2 S e 3 and doped films exhibited reverse saturated absorption (RSA), and the occurrence of the reverse saturated absorption behavior of the doped films was mainly due to two-photon absorption (TPA), free carrier absorption (FCA), and the presence of defective energy levels. Compared with pure S b 2 S e 3 films, N i-S b 2 S e 3 films exhibit significantly enhanced nonlinear absorption properties and nonlinear refractive properties. By increasing Ni sputtering power and incident laser energy, the nonlinear optic properties of N i-S b 2 S e 3 films are enhanced. By testing the sample films using SEM, XRD, and UV-Vis techniques, we found that Ni metal doping greatly improved and optimized the crystallinity of the films and adjusted the optical band gap.

Mixed Rare-Earth Chalcogenide Borate Eu9-xRExMgS2B20O41 (RE = Sm, Gd) Featuring a 3D {[B20O41]22-}∞ Framework Connected by [B6O9(O0.5)6]6- and [B7O13(O0.5)3]8- Clusters

Rare-earth (RE) chalcogenide borates are very rarely discovered in view of the difficulties in synthesis though they have demonstrated attractive physical performances. Here, the first mixed RE chalcogenide borates Eu_5.4Sm_3.6MgS₂B₂₀O₄₁ (1) and Eu₃Gd₆MgS₂B₂₀O₄₁ (2) are synthesized by combining RE, sulfur, and borate ions into one structure. They crystallize in the centrosymmetric hexagonal space group P6₃/m, and their 3D honeycomb-like {[B₂₀O₄₁]^22-}_∞ open frameworks are built by [B₆O₉(O_0.5)₆]^6- and [B₇O₁₃(O_0.5)₃]^8- polyanionic clusters and consolidated by Mg²⁺ ions; both of which are formed by BO₄ tetrahedra and BO₃ planar triangles. The coordination modes of RE ions are rare REO₆S₂ bicapped trigonal prisms and REO₈S irregular polyhedra, and their band gaps are determined to be 2.25 and 2.22 eV, respectively. They exhibit antiferromagnetic interactions and distinct photocurrent responses. The corresponding theoretical calculations are also performed. The study of 1 and 2 perhaps stimulates interest in exploring new functional RE chalcogenide borates.

Rational Design of a Rare-Earth Oxychalcogenide Nd3 [Ga3 O3 S3 ][Ge2 O7 ] with Superior Infrared Nonlinear Optical Performance

Inorganic chalcogenides have been studied as the most promising infrared (IR) nonlinear optical (NLO) candidates for the past decades. However, it is proven difficult to discover high-performance materials that combine the often-incompatible properties of large energy gap (E_g ) and strong second harmonic generation (SHG) response (d_eff ), especially for rare-earth chalcogenides. Herein, centrosymmetric Cs₃ [Sb₃ O₆ ][Ge₂ O₇ ] is selected as a maternal structure and a new noncentrosymmetric rare-earth oxychalcogenide, namely, Nd₃ [Ga₃ O₃ S₃ ][Ge₂ O₇ ], is successfully designed and obtained by the module substitution strategy for the first time. Especially, Nd₃ [Ga₃ O₃ S₃ ][Ge₂ O₇ ] is the first case of breaking the trade-off relationship between wide E_g (>3.5 eV) and large d_eff (>0.5 × AgGaS₂ ) in rare-earth chalcogenide system, and thus displays an outstanding IR-NLO comprehensive performance. Detailed structure analyses and theoretical studies reveal that the NLO effect originates mainly from the cooperation of heteroanionic [GaO₂ S₂ ] and [NdO₂ S₆ ] asymmetric building blocks. This work not only presents an excellent rare-earth IR-NLO candidate, but also plays a crucial role in the rational structure design of other NLO materials in which both large E_g and strong d_eff are pursued.

Oxychalcogenides: A Promising Class of Materials for Nonlinear Optical Crystals with Mixed-Anion Groups

Infrared nonlinear optical (IR NLO) materials are of great significance in the development of IR laser technology. But rationally designing high-performance IR NLO materials remains a huge challenge due to the conflict between the necessary properties required for NLO materials. Notably, oxychalcogenides with mixed-anion groups have drawn extensive interest as a family of important IR NLO candidates because they integrate the property advantages of oxides and chalcogenides by chemical substitution engineering. In this review, we provide a survey of reported oxychalcogenides and aim to present the development of NLO oxychalcogenides from the perspective of rational design of their structural chemistry. Furthermore, we focus on the relationships between partial substitution and structural symmetry as well as optical properties. These provide some helpful guidance for the further exploration and design of novel oxychalcogenide materials with excellent NLO performance in the future.

Ba5Ga2SiO4S6: a Phase-Matching Nonlinear Optical Oxychalcogenide Design via Structural Regulation Originated from Heteroanion Introduction

Tailored structural regulation to obtain a new non-centrosymmetric (NCS) compound with excellent optical properties is highly desirable but remains a challenge for nonlinear optical (NLO) material design. In this work, centrosymmetric celsian-type BaGa₂Si₂O₈ was selected as a template structure, and a novel NCS oxychalcogenide, namely, Ba₅Ga₂SiO₄S₆, was successfully designed via the introduction of heteroanions under high-temperature solid-state conditions. Ba₅Ga₂SiO₄S₆ adopts the monoclinic space group of Cc (no. 9) and is formed by charges balancing Ba²⁺ cations and discrete [Ga₂SiO₄S₆] clusters made of corner-sharing [SiO₄] and [GaOS₃] tetrahedra. Notably, Ba₅Ga₂SiO₄S₆ exhibits the critical requirements as a potential UV NLO candidate, including a phase-matching second-harmonic generation intensity (∼1.0 × KDP), a beneficial laser-induced damage threshold (1.2 × KDP), a large birefringence (Δn = 0.10@546 nm), and a short UV absorption cutoff edge (ca. 0.26 μm). Furthermore, the theoretical calculation is implemented to provide a deeper analysis of the structure-activity relationship. The investigated example of structural regulation originated from heteroanion introduction in this study may offer a feasible strategy for high-performance NLO candidate design.

Characterizations and Nonlinear-Optical Properties of Pentanary Transition-Metal Oxysulfide Sr2CoGe2OS6

As one type of material containing multiple anions, oxysulfides can combine the advantages of oxides and sulfides and are deeply studied as nonlinear-optical (NLO) materials. Herein, a new melilite-type pentanary oxysulfide Sr₂CoGe₂OS₆ is studied. It crystallizes in the noncentrosymmetric tetragonal space group P4̅2₁m, and its structure features GeOS₃ and CoS₄ tetrahedra-built {[CoGe₂OS₆]^4-}_∞ layers. Its powder sample exhibits a moderate phase-matchable NLO response and a high laser-induced damage threshold. The NLO response is mainly determined by CoS₄ tetrahedra according to the theoretical calculation results. This work indicates that transition-metal oxysulfides can also be considered as potential infrared NLO materials.

Oxychalcogenides as Promising Ultraviolet Nonlinear Optical Candidates: Experimental and Theoretical Studies of AEGeOS2 (AE = Sr and Ba)

Oxychalcogenides have gained widespread attention as promising infrared nonlinear optical (IR-NLO) candidates. However, high-performance oxychalcogenides have rarely been reported in the ultraviolet (UV) region owing to the low energy gaps (E_g < 4.0 eV). Herein, two non-centrosymmetric (NCS) oxychalcogenides with one-dimensional (1D) chain structures and wide E_g (>4.3 eV), namely, AEGeOS₂ (AE = Sr and Ba), have been discovered by combined experiments and theory calculations as a new source of UV-NLO materials. Significantly, they exhibit excellent comprehensive performance comparable to the commercial UV-NLO material KH₂PO₄ (KDP), including large phase-matching ranges (>380 nm), sufficient second harmonic generation intensities (0.7-1.1 × KDP), high laser-induced damage thresholds (1.2 × KDP), wide transparent regions (0.26-12.2 μm), and good thermal stability (up to 1100 K). Moreover, systematic structure-activity relationship analysis illustrates that the 1D homochiral helical [GeOS₂]^2- chains composed of heteroanionic [GeS₂O₂] units make major contribution to the desirable UV-NLO performance. This work makes the two compounds shine out as new energy in the UV-NLO field and offers a new perspective for the exploration of structure-driven functional oxychalcogenides.

Mixed-Anion-Oriented Design of LnMGa3S6O (Ln = La, Pr, and Nd; M = Ca and Sr) Nonlinear Optical Oxysulfides with Targeted Property Balance

Nonlinear optical (NLO) crystals are of importance on extending infrared (IR) laser wavelengths. Considering their performance drawbacks in commercial IR NLO crystals, a recent challenge in exploring new excellent IR NLO crystals is how to break the inherent conflict between a wide bandgap (E_g ≥ 3.0 eV) and large NLO effect (d_ij ≥ 0.5 × AgGaS₂) and simultaneously enlarge the birefringence (Δn) for a requisite phase-matching (PM) behavior. For that reason, rational combination of mixed-anion functional groups into a crystal structure affords the successful design and synthesis of six LnMGa₃S₆O (Ln = La, Pr, and Nd; M = Ca and Sr) NLO oxysulfides. Among them, LaMGa₃S₆O satisfy the property-balance demand (E_g: 3.21-3.27 eV and d_ij: 0.9-1.0 × AgGaS₂) as promising PM NLO crystals through gathering their property advantages between LaMGa₃O₇ and LaMGa₃S₇ by mixed-anion-oriented performance engineering. A study on the structure-property relationship indicates that heteroleptic (Ln/M)S₇O and GaS₃O anionic groups are proven as promising NLO-active units and offer a great synergistic effect on the NLO origin. This work as a visualized model not only provides a first clear cognition on varying properties from oxide to sulfide to oxysulfide but also highlights the feasibility of mixed-anion-oriented design of new NLO candidates with balanced performances.

Sr3 [SnOSe3 ][CO3 ]: A Heteroanionic Nonlinear Optical Material Containing Planar π-conjugated [CO3 ] and Heteroleptic [SnOSe3 ] Anionic Groups

Inorganic heteroanionic materials are attracting increasing attention for exploring new nonlinear optical (NLO) materials because they could better satisfy the necessary but conflicting properties of NLO crystals, e.g. large SHG response and wide band-gap. Up to now, the reports on heteroanionic NLO materials have mainly focused on ultraviolet or visible oxide-based fluoroborates, fluorophosphates, borate-phosphates and borate-iodates. However, chalcogenides containing different kinds of anionic groups have barely been reported. Herein, we have synthesized the first oxychalcogenide-carbonate, Sr₃ [SnOSe₃ ][CO₃ ] that contains two different kinds of anionic groups, [SnOSe₃ ] and [CO₃ ]. It crystallizes in a noncentrosymmetric space group and exhibits fascinating NLO properties, including a large SHG response (≈1×AGS), sufficient birefringence (0.12 @1064 nm), wide band-gap (3.46 eV) and high laser damage threshold (240 MW cm^-2 ). These make Sr₃ [SnOSe₃ ][CO₃ ] a promising NLO crystal.

Quaternary Noncentrosymmetric Rare-Earth Sulfides Ba4RE2Cd3S10 (RE = Sm, Gd, or Tb): A Joint Experimental and Theoretical Investigation

Multinary rare-earth chalcogenides with d-block transition metals have attracted considerable attention owing to their intriguing structural architectures and promising practical applications. In this work, three quaternary rare-earth sulfides, Ba₄RE₂Cd₃S₁₀ (RE = Sm, Gd, or Tb), have been obtained by the high-temperature solid-state method. These compounds are isostructural and belong to the noncentrosymmetric orthorhombic space group Cmc2₁ (No. 36). The basic structural unit contains unique two-dimensional anionic [RE₂Cd₃S₁₀]^8- layers, which are separated by Ba²⁺ cations. Remarkably, Ba₄Sm₂Cd₃S₁₀ exhibits a high second-harmonic-generation intensity (1.8 times that of AgGaS₂) and a significantly higher laser-induced damage threshold (14.3 times that of AgGaS₂), which is the first case possessing an infrared (IR) nonlinear optical (NLO) property in the quaternary AE/RE/TM/Q (AE = alkaline-earth metals; RE = rare-earth metals; TM = d-block transition metals; and Q = chalcogen) systems. Moreover, theoretical investigations of the structure-property relationship indicate that the combined action of various types of NLO-active units makes the main contribution to the SHG activity. This discovery may shed light on broadening the frontiers of IR-NLO materials.

Rational Design of a Promising Oxychalcogenide Infrared Nonlinear Optical Crystal

Oxychalcogenides with the performance-advantages of both chalcogenides and oxides are emerging materials class for infrared (IR) nonlinear optical (NLO) crystals that can expand the wavelength of the solid-state laser to...

Synthesis, structural evolution and optical properties of a new family of oxychalcogenides [Sr3VO4][MQ3] (M = Ga, In, Q = S, Se)

New oxychalcogenides [Sr3VO4][MQ3] (M = Ga, In, Q = S, Se) were successfully synthesized. The Ga analogues feature a 0-D structure containing isolated [Ga2Q6]6− dimers, while the In analogues feature a 1-D structure containing ∞[InQ3]3− chains.

From oxides to oxysulfides: the mixed-anion GeS3O unit induces huge improvement in the nonlinear optical effect and optical anisotropy for potential nonlinear optical materials

Oxysulfides combining intrinsic performance advantages between sulfides (strong NLO response) and oxides (wide optical bandgap) are proposed as potential infrared (IR) NLO materials. Theoretical calculation shows that the mixed-anion GeS₃O tetrahedron has a stronger polarizability anisotropy and hyperpolarizability than that of the typical GeO₄ unit. Based on this, two Sr₂MGe₂S₆O (M = Zn, Cd) oxysulfides with the GeS₃O unit show dozens of times improvement in critical birefringence and the NLO effect compared with those of isostructural Sr₂ZnGe₂O₇. Moreover, structure–property study further verifies that the mixed-anion GeS₃O ligand is a useful NLO-active unit and can offer great influence over the NLO origin. This research result also gives us a feasible design strategy and research system to explore new IR NLO candidates.

The mixed-anion GeS₃O unit induces huge improvement in the optical anisotropy and NLO response from Sr₂ZnGe₂O₇ oxide to Sr₂MGe₂S₆O oxysulfides.

La3 Ga3 Ge2 S3 O10 : An Ultraviolet Nonlinear Optical Oxysulfide Designed by Anion-Directed Band Gap Engineering

Chalcogenide-containing compounds have been widely studied as infrared nonlinear optical (NLO) materials. However, they have never been applied in the ultraviolet (UV) region owing to the high energy levels of chalcogen anions, leading to band gap narrowing. We report the synthesis of a new UV NLO oxysulfide La₃ Ga₃ Ge₂ S₃ O₁₀ with an exceptionally wide band gap of 4.70 eV due to from the unique anion-ordered frameworks comprising 1D ¹ _∞ [(Ga_3/5 Ge_2/5 )₃ S₃ O₃ ] triangular tubes and 0D (Ga_3/5 Ge_2/5 )₂ O₇ dimers of corner-sharing (Ga/Ge)S₂ O₂ and (Ga/Ge)O₄ tetrahedra, respectively. Second harmonic generation (SHG) measurements revealed that La₃ Ga₃ Ge₂ S₃ O₁₀ was phase matchable with twice the SHG response of KH₂ PO₄ . The results of theoretical calculations suggest that the strong SHG response is mainly attributable to the S-3p and O-2p orbitals in the occupied states. The anion-directed band-gap engineering may give insights into the application of NLO oxychalcogenides in the UV regions.

A high dimensional oxysulfide built from large iron-based clusters with partial charge-ordering

Herein we report the original Ba₁₀Fe_7.75Zn_5.25S₁₈Si₃O₁₂ oxysulfide which crystallizes in a new structural type. Contrary to the usual oxychalcogenides, it crystallizes with a non-centrosymmetric 3D spatial network structure built from large magnetic clusters consisting of twelve (Fe^2+/3+/Zn)S₃O tetrahedra decorating a central Fe²⁺S₆ octahedron and exhibiting a spin glass state.

The Rise of Infrared Nonlinear Optical Pnictides: Advances and Outlooks

Infrared (IR) nonlinear optical (NLO) materials are the core devices to realize IR laser output, which are of vital importance in civilian and military fields. Non-centrosymmetric chalcogenide and pnictide compounds have already been widely accepted as favorable systems for IR-NLO materials. Compared to the extensively investigated IR-NLO chalcogenides during the past few decades, the research of non-centrosymmetric phosphides as IR-NLO materials is relatively scarce. In this frontier article, the recent progress of pnictides as emerging IR-NLO candidates has been highlighted based on the perspective of new crystal exploration. These IR-NLO pnictides recently reported were divided into three groups from binary to quaternary according to their chemical compositions. The synthetic methods, structural chemistry, and structure-activity relationships are analyzed and summarized in detail. Finally, current problems and the future development of this field are also proposed.

Structural Transformation and Second-Harmonic-Generation Activity in Rare-Earth and d0 Transition-Metal Oxysulfides RE3NbS3O4 (RE = Ce, Sm, Gd, Dy)

Investigations of inorganic compounds with mixed anions have drawn much attention. Here, three oxysulfides, Sm₃NbS₃O₄ (1), Gd₃NbS₃O₄ (2), and Dy₃NbS₃O₄ (3), are obtained by solid-state reactions. 1 and 2 crystallize in the polar space group Pna2₁, while 3 crystallizes in the centric space group Pnma. The anionic frameworks of 1 and 2 are built by isolated distorted [NbS₂O₄]^7- octahedra, while [NbS₃O₄]^9- is used for 3. 1 and 2 exhibit phase-matchable second-harmonic-generation (SHG) effects of about 0.3 and 0.4 × AGS at 2.1 μm. The [NbS₂O₄]^7- octahedron was first used as a SHG-active motif for nonlinear-optical (NLO) materials. A systematic analysis of the transformation between these crystal structures, NLO performances, and magnetic behaviors, as well as first-principles theoretical studies, is presented. This work enriches the study on relatively rarely explored NLO-active metal oxysulfides.

AZn4Ga5Se12 (A = K, Rb, or Cs): Infrared Nonlinear Optical Materials with Simultaneous Large Second Harmonic Generation Responses and High Laser-Induced Damage Thresholds

Despite the fact that nonlinear optical (NLO) crystals such as AgGaS₂ and AgGaSe₂ have been widely used in the infrared (IR) range due to their large second harmonic generation (SHG) coefficients and wide range of IR transparency windows, the small laser-induced damage threshold (LIDT) remains a great issue hindering their high-power applications. Herein, three noncentrosymmetric (NCS) chalcogenides AZn₄Ga₅Se₁₂ (A = K, Rb, or Cs) are successfully obtained through an appropriate flux method after the extensive design and synthesis of the A/Zn/Ga/Q system. Single-crystal X-ray diffraction data demonstrate that they adopt trigonal space group R3 (No. 146) with three-dimensional diamond-like frameworks composed of [M₉Se₂₄] layers (M = Zn or Ga) stacking in the same direction and filled by charge-balancing A⁺ cations. Noticeably, they all exhibit strong powder SHG responses (2.8-3.7 × AgGaS₂) and amazing LIDTs (19.2-23.4 × AgGaS₂). In addition, theoretical calculations are performed to further determine the relationship between NCS structures and NLO properties. This work provides effective solutions for overcoming the trade-off between strong SHG and high LIDT in IR-NLO materials.

Ba2Ge2Te5: a ternary NLO-active telluride with unusual one-dimensional helical chains and giant second harmonic-generation tensors

The linear-optical and NLO properties of a ternary NLO-active telluride, Ba2Ge2Te5, were investigated systematically at the experimental and theoretical levels for the first time.