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Deep ultraviolet (DUV) nonlinear optical (NLO) crystals have important applications in lithography, microfabrication, and high-resolution photoelectric spectrometer. In recent years, significant progress has been made in both the theoretical design and experimental research of DUV NLO crystals. This review aims to offer a comprehensive perspective on exploring a new generation of DUV NLO materials. First, we summarize various computer-aided strategies for crystal structure design and emphasize their significant role in advancing the discovery of DUV NLO materials. Then, we outline several representative DUV crystals of experimental synthesis. Finally, we discuss the future prospects for exploring new generations of DUV NLO materials. We believe that employing data-driven, computer-aided methods to explore DUV NLO materials will help address the current challenges in the field of DUV NLO materials research. The close integration of calculation and experimentation will unlock new opportunities. [ABSTRACT FROM AUTHOR]

Nonlinear optical (NLO) crystals that can expand the spectral range of laser outputs have attracted significant attention for their optoelectronic applications. The research progress from the discovery of new single crystal structures to the realization of final device applications involves many key steps and is very time consuming and challenging. Consequently, exploring efficient design strategies to shorten the research period and accelerate the rational design of novel NLO materials has become imperative to address the pressing demand for advanced materials. The recent shift in paradigm toward exploring new NLO crystals involves significant progress from extensive "trial and error" methodologies to strategic approaches. This review proposes the concept of rational structure design for nonlinear optical crystals leveraging advantageous templates. It further discusses their optical characteristics, promising applications as second-order NLO materials, and the relationship between their structure and performance, and highlights urgent issues that need to be addressed in the field of NLO crystals in the future. The review aims to provide ideas and driving impetus to encourage researchers to achieve new breakthroughs in the next generation of NLO materials. [ABSTRACT FROM AUTHOR]

Ultraviolet (UV) and Deep‐UV (DUV, λ<200 nm) nonlinear optical (NLO) materials play a significant role to convert the wavelength of laser for producing UV/DUV coherent light in the laser industry. The Al [Ne]3s23p1 atom with empty d orbitals can form sp3, sp3d, and sp3d2 hybrid orbitals when bonding with O/F atoms, which leads to the construction of [AlOmFn] (m+n=4, 5, 6) units. Therein, aluminoborates have received intensive attention due to the effective structural and functional adjustment effects of the diverse Al−O/F units. Accordingly, numerous aluminoborates as candidates for the next generation of UV/DUV NLO materials were discovered. In this review, recently discovered aluminoborates are overviewed and analyzed, including their syntheses, crystal structure features, and second‐order NLO performances. We aim to provide the latest progress and outlook on the crystal chemistry of aluminoborates and boost the finding of the next NLO candidates with high performances. [ABSTRACT FROM AUTHOR]

Design and exploratory synthesis of new mid‐infrared (mid‐IR) nonlinear optical (NLO) materials are urgently needed for modern laser science and technology because the widely used IR NLO crystals still suffer from their inextricable drawbacks. Herein, a multi‐level data‐driven approach to realize fast and efficient structure prediction for the exploration of promising mid‐IR NLO materials is proposed. Techniques based on machine learning, crystal structure prediction, high‐throughput calculation and screening, database building, and experimental verification are tightly combined for creating pathways from chemical compositions, crystal structures to rational synthesis. Through this data‐driven approach, not only are all known structures successfully predicted but also five thermodynamically stable and 50 metastable new selenides in AIBIIISe2 systems (AI = Li, Na, K, Rb, and Cs; BIII = Al and Ga) are found, among which eight outstanding compounds with wide bandgaps (> 2.70 eV) and large SHG responses (>10 pm V−1) are suggested. Moreover, the predicted compounds I4¯2d‐LiGaSe2 and I4/mcm‐KAlSe2 are successfully obtained experimentally. In particular, LiGaSe2 exhibits a robust SHG response (≈2 × AGS) and long IR absorption edge that can cover two atmospheric windows (3–5, 8–12 µm). Simultaneously, this new research paradigm is also applicative for discovering new materials in other fields. [ABSTRACT FROM AUTHOR]

Fluorine-containing compounds significantly enrich the diversity of inorganic chemical structures. Here, four alkaline-earth metal difluorophosphates with different space groups, namely NH4Mg(PO2F2)3 (Cmcm) (1), NH4Sr(PO2F2)3 (P1¯) (2), (NH4)2Ba(PO2F2)4 (P2/n) (3) and Ba(PO2F2)2 (I4¯2d) (4), were synthesized and their structures were determined for the first time. 4 is not only the first alkaline-earth-metal difluorophosphate, but also the first difluorophosphate reported to crystallize in the non-centrosymmetric space group I4¯2d of the tetragonal crystal system. All of the three-dimensional (3D) structures of the title compounds consist of isolated (PO2F2)−, AE–O and NH4+ units, while the differences of the cation radius result in various arrangements of the (PO2F2)− units, which leads to diverse crystal structures and the disparate optical anisotropy of the crystals. According to the deep-ultraviolet (DUV) transmittance spectrum, 3 exhibits a short DUV cut off edge (<180 nm). Solid state 19F and 31P magic-angle spinning NMR spectroscopy was used to verify the presence of covalent P–F bonds in 3. The different size effects, as well as the coordination environments of the Mg2+, Sr2+, and Ba2+ cations, on the structures as a whole have been discussed in detail. In addition, the calculated birefringence values were observed to differ from 0.011 to 0.033 for the four compounds. [ABSTRACT FROM AUTHOR]

Deep‐ultraviolet nonlinear optical (DUV NLO) materials are attracting increasing attention because of their structural diversity and complexity. Using the two‐dimensional (2D) crystal structure prediction method combined with the first‐principles calculations, here we propose layered 18‐membered‐ring (18MR) boron oxide B2O3 polymorphs as high‐performance NLO materials. 18MR‐B2O3 with the AA and AB stackings are potential DUV NLO materials. The superior performing 18MR‐B2O3AB has an unprecedentedly high second harmonic generation coefficient of 1.63 pm V−1, the largest among the DUV NLO materials, three times larger than that of the advanced DUV NLO material KBe2BO3F2 and comparable to that of β‐BaB2O4. Its unusually large birefringence of 0.196 at 400 nm guarantees the phase‐matching wavelength λPM to reach this material's extreme absorption edge of ≈154 nm. [ABSTRACT FROM AUTHOR]

A new compound, namely (NH4)3PbCl5, has been synthesized via a low-temperature molten salt method in a closed system. It crystallizes in the orthorhombic Pnma (No. 62) space group. The crystal structure of (NH4)3PbCl5 features a distinct three-dimensional network constructed via hydrogen bonds that exist between ammonium and chloride anions. The UV-Vis-NIR diffuse reflectance spectrum displays a short UV cutoff edge at about 256 nm. Besides, the thermal behavior (TG and DSC) was also analyzed. To better understand the structure–property relationships of (NH4)3PbCl5, theoretical calculations based on density functional theory were also performed. The result shows that the birefringence is expected to be about 0.050 at 1064 nm, and the bandgap is about 4.45 eV, which is consistent with the experimental result. [ABSTRACT FROM AUTHOR]

Mixed-anion compounds are among the most promising systems to design functional materials with enhanced properties. Among the phosphate–sulfate species, the [SO4]2− and [PO2F2]− tetrahedra are known and give rise to structural versatility. However, to date, the crystal structures of phosphate–sulfates with the coexistence of two distinct anion groups ([S2O7]2− and [PO2F2]−) in one compound are unknown. Here, a novel type of fluorooxophosphorsulfate, K4(PO2F2)2(S2O7) (KSPOF), is designed and synthesized via a high-temperature method in a closed system. The crystal structure is derived from single-crystal X-ray diffraction (C2/c, a = 13.000(10) Å, b = 7.5430(10) Å, c = 19.010(10) Å, β = 130.070(10)°, and Z = 4). It is the first fluorooxophosphorsulfate with mixed-anion building units ([S2O7]2− and [PO2F2]−) and a unique drum-like cluster was found, which enriches the diversity of structures for fluorooxophosphorsulfate systems. Furthermore, the theoretical calculations indicate that KSPOF possesses moderate birefringence, which mainly originates from the distorted [PO2F2]− tetrahedron. [ABSTRACT FROM AUTHOR]

In contrast to the well‐investigated halogen‐containing borates and carbonates, very few halogen‐containing borate carbonate compounds have been reported. Specifically, no example of borate carbonate fluoride has been synthesized successfully until now. Herein, the planar π‐conjugated units [BO3]3− and [CO3]2− and the F− ions are introduced simultaneously into one crystal structure resulting in the first borate carbonate fluoride, Ba3(BO3)(CO3)F, by the high‐temperature solution method in the atmosphere. Its structure features a hexagonal channel formed by the [BO3]3− and [CO3]2− units with the [F3Ba8]13+ trimers filled in the channel. Various characterizations including single crystal‐ and powder‐XRD, EDX, IR, UV‐vis‐NIR, and TG‐DSC, together with the first principles calculation have been carried out to verify the structure and fully understand the structure–property relationships. [ABSTRACT FROM AUTHOR]

In minerals and artificial crystals, the OH and F groups often coexist and have a high probability of disordered structure. The OH/F position cannot be determined accurately in the crystal structure only by the direct X-ray diffraction method because of the poor contrast between O and F and the weak diffractivity of hydrogen atoms. In this work, a new fluorooxoborate Ba[B2OF3(OH)2]2, with a size of up to 12 × 4 × 3 mm3, has been synthesized successfully by a facile hydrothermal reaction. The BOF3 units with well-ordered OH/F positions are observed for the first time in alkali/alkaline earth metal fluorooxoborates. Owing to the selective fluorination of BO4, Ba(B2OF3(OH)2)2 exhibits a large birefringence and hence can be used as a DUV birefringent material. This work will guide the study of the structural chemistry of oxyfluorides. [ABSTRACT FROM AUTHOR]

A new hydrated magnesium borate, Mg(H2O)6B4O5(OH)4(H2O)3, was synthesized successfully by a facile slow evaporation method. Its structure was determined by single crystal X-ray diffraction, and it contains the functional building block (FBB) [B4O5(OH)4]. It possesses a short DUV cutoff edge (<175 nm) which benefits from the absence of dangling bonds in the crystal structure. Its properties were analyzed by IR spectroscopy and UV-vis-NIR diffuse reflectance spectroscopy. Moreover, theoretical calculations were carried out to analyze the relationship between the electronic structure and optical properties. [ABSTRACT FROM AUTHOR]

The crystal structure of diamagnetic borate chloride Sn2B5O9Cl exhibits two crystallographically independent tin sites which both show pronounced lone-pair activity of the tin atoms. This is reflected in substantial quadrupole splitting in the 119Sn Mössbauer spectrum. The isomer shifts of 3.887(8) and 4.137(7) mm s−1 clearly indicate divalent tin. In agreement with bond valence calculations, the Sn1 atoms have a lower charge and the higher isomer shift, compatible with a higher electron density at the tin nuclei. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Special review on the IR NLO materials with balanced properties is systematically reported. • Relationship between microscopic groups and material performances is analyzed. • Efficient strategies toward design of new promising IR NLO materials are provided. Abstract Infrared (IR) lasers have been widely applied in the many military and civil fields. Nonlinear optical (NLO) crystals have been developed as the critical materials to achieve the efficient IR laser output by the typical frequency-conversion technology. However, commercial IR NLO materials are seriously limited in the IR region because of their low laser-damage thresholds (LDTs) or harmful two-photon absorption (TPA). Therefore, the discovery of new IR NLO materials with optimal key performances (concurrently large NLO coefficient (d ij) and wide optical bandgap (E g)) has become imperative. Recently, metal chalcogenides have become a rich source for exploration of IR NLO materials and hundreds of them have been discovered. Based on the good balance between experimental E g (≥3.0 eV) and d ij (≥0.5 × AgGaS 2) required for one IR NLO material, to our best knowledge, about 49 chalcogenides satisfy the above condition while limiting the scope to the equal or greater than ternary system. We focus on the structure-performance relationship for 49 compounds and the result shows that alkali or/and alkaline earth metals must be the preferred cations to maintain the wide E g. Besides, their critical anionic groups are summarized and shown as follows: (i) typical tetrahedral MIIIQ 4 (MIII = Ga, In) or/and MIVQ 4 (MIV = Si, Ge; Q = S, Se) or PS 4 units; (ii) d 10 elements-centered (MIIQ 4 : MII = Zn, Cd) and typical MIIIQ 4 or MIVQ 4 tetrahedra; (iii) halogen-centered polyhedral ligands. So the combination of above anionic groups and alkali or/and alkaline earth metals into crystal structures produces the feasible design strategy to explore new IR NLO materials with excellent performances. [ABSTRACT FROM AUTHOR]

Abstract: Two new alkaline earth metal fluorooxoborates, CaB4O6F2 and SrB4O6F2, have been synthesized and characterized. The title compounds are isostructural and crystallize in centrosymmetric space group P 1 ‾ (No. 2). Structurally, the fundamental building blocks, B4O8F2 groups, are connected by B−O bonds to form [B4O6F2]∞ layers, which stack parallelly along the c axis. In addition, BaB4O6F2, a known fluorooxoborate with different crystal structure, was also synthesized and characterized for comparison. The cation size influence on the structure of this MB4O6F2 (M=Ca, Sr, Ba) family is discussed in detail. The diffuse‐reflectance spectroscopy measurements indicate that the cutoff edges of title compounds are below 190 nm. Moreover, first‐principle calculation results demonstrate that MB4O6F2 (M=Ca, Sr, Ba) have large birefringence of 0.091, 0.089, and 0.085 at 1064 nm. Both experimental and theoretical studies suggest that MB4O6F2 (M=Ca, Sr, Ba) are promising birefringent materials for deep‐UV applications. [ABSTRACT FROM AUTHOR]

A new telluro-phosphate K2TeP2O8 was synthesized by a high temperature solution method. It crystallizes in the orthorhombic space group P21212 and features a [TeP2O8]2− layer structure, which is the first layer structure built by Te–O and P–O groups among the telluro-phosphates. More interestingly, the layer structure in K2TeP2O8 is nearly pentagonal. First-principles theoretical calculations suggest that K2TeP2O8 possesses a large birefringence compared to phosphates. Furthermore, IR spectra, UV-vis-NIR diffuse reflectance spectroscopy data, thermal behavior, and electronic structure calculations were studied. [ABSTRACT FROM AUTHOR]

Abstract: The large number and structural beauty of silicates are largely due to the variety of connection mode of SiO4 tetrahedra. SiO6 and SiF6 octahedra are also known and give rise for structural versatility of inorganic silicates. However, to date, the crystal structure of inorganic fluorooxosilicates with oxofluoride SiOxF4−x or SiOxF6−x species are unknown. Now, fluorine was successfully introduced into the silicophosphates, and the first fluorooxosilicophosphate K4Si3P2O7F12 with an unprecedented SiO2F4 species was synthesized. The existence of Si−F bonds was verified by comprehensively experimental and theoretical work. Using ab initio and bond valence calculations, the oxofluoride SiOxF6−x species is shown to be stable when oxygen atoms connect to other atoms with strong covalent interactions. This work will contribute to the structural diversity of silicate chemistry by the exploration of the new fluorooxosilicates. [ABSTRACT FROM AUTHOR]

Abstract: Two new non‐centrosymmetric ternary compounds, MgSiAs2 and Mg3Si6As8, are discovered via metal flux and solid‐state synthetic methods. MgSiAs2 belongs to the well‐known II‐IV‐V2 family, which is extensively studied experimentally and computationally for their optical properties. MgSiAs2 is computationally predicted but not experimentally known prior to this work. Mg3Si6As8 crystallizes in a new non‐centrosymmetric cubic chiral structure type with the Pearson symbol cP68. The syntheses, crystal structure, thermal and chemical stabilities, electronic structures, and optical properties of these two new compounds are investigated in this work. Optical absorption measurements and electronic structure calculations reveal the two compounds to be direct or pseudo‐direct bandgap semiconductors (1.8–2 eV). The crystal structures of both compounds are non‐centrosymmetric, though Mg3Si6As8 belongs to the 432 chiral crystal class, which is optically active but does not exhibit second harmonic generation (SHG) behavior. The SHG response of MgSiAs2 is 60% of that for AgGaS2, but MgSiAs2 exhibits a higher laser damage threshold than AgGaS2 at 33.2 MW cm−2. [ABSTRACT FROM AUTHOR]

Abstract: Introducing fluorine into borates indicates the direction for structural evolution. A new fluorooxoborate, NaRbB6O9F2 featuring a unique [B6O9F2]∞ layered structure and excellent optical properties has been synthesized. It is further demonstrated that incorporation of fluorine can enrich the structural chemistry of borates. [ABSTRACT FROM AUTHOR]

Three new alkali metal molybdate crystals LiRbMo3O10, LiCsMo3O10 and KCsMo3O10 have been synthesized, and their structures have been determined by single-crystal X-ray diffraction. LiRbMo3O10 and LiCsMo3O10 are isostructural and crystallize in the orthorhombic space group Pnma, whereas KCsMo3O10 belongs to the space group P1̅. Moreover, we have also obtained NaCsMo3O10 crystal, and its unit cell dimensions have been previously reported. Crystallographic analysis reveals that NaCsMo3O10 crystallizes in the space group Pnma. The effect of cations size on their framework structures has been discussed in detail. In addition, infrared spectra are used to verify their structural validity. Furthermore, the UV-Vis-NIR diffuse reflectance spectra are also presented. Finally, the first-principle theoretical studies are carried out to increase the understanding of electronic structures and linear optical properties. [ABSTRACT FROM AUTHOR]

The discovery of new nonlinear optical (NLO) materials for coherent light generation in the deep-ultraviolet (DUV, wavelength below 200 nm) region is essential for the development of laser technologies. Herein, we report a new material CsB4O6F (CBF), which combines the superior structural properties of two well-known NLO materials, β-BaB2O4 (BBO) and KBe2BO3F2 (KBBF). CBF exhibits excellent DUV optical properties including a short cutoff edge (155 nm), a large SHG response (≈1.9×KDP), and a suitable birefringence that enables frequency doubling down to 171.6 nm. Remarkably, CBF melts congruently and shows an improved growth habit. In addition, our rational design strategy will contribute to the discovery of DUV NLO materials. [ABSTRACT FROM AUTHOR]

Generally, sulfur is inclined to combine with oxygen to form sulfate ions in a solid-state reaction. Interestingly, an extraordinary sulfide silicate, Na6Si3S8O, was successfully obtained in a vacuum-sealed silica tube for the first time. Its crystal structure features novel 1D straight chains formed by the interconnection of tri-polymerized [Si3S8O]6− and [Na4S5O]11− units, demonstrating the first sulfide silicate exhibiting S–Na–O and S–Si–O connections without S–O bonds. Moreover, Na6Si3S8O is also verified as a promising birefringent material owing to its large birefringence (Δn = 0.215–0.094 from 0.3 to 4.0 μm). [ABSTRACT FROM AUTHOR]

Five new mixed-metal borate crystals, namely, K2BaB16O26, K3CsB20O32, Na2Cs2BaB18O30, Na2Rb2PbB18O30, and Na2Cs2PbB18O30, have been synthesized by the high-temperature solution method. These structures were characterized by single-crystal X-ray diffraction and their B−O configurations are shown to feature complicated three-dimensional (3D) open-framework structures incorporating different types of channels. For all five compounds, the frameworks can be reduced to four-connected (4-c) uninodal nets with sra-, dia- and nbo-type topologies by assigning the [B5O10]5− and [B3O7]5− clusters as basic nodes. First-principles calculations have shown that the multiple cations in mixed-metal borates influence the ground-state electronic structures and associated optical absorptions. In addition, the crystal structures, thermal stabilities, and IR spectra of the title compounds have also been performed. [ABSTRACT FROM AUTHOR]

Combining different functional units together has been regarded as the most ideal strategy to design and synthesize new inorganic materials. Based on numerous experiments, it was possible to assemble three kinds of anion groups together and find a series of novel mixed borate and carbonate halides, Rb9[B4O5(OH)4]3(CO3)X ⋅7 H2O (X=Cl, Br, and I) and K9[B4O5(OH)4]3(CO3)X ⋅7 H2O (X=OH and I). Based on the structural template of these compounds, we also obtained the NaRb6[B4O5(OH)4]3X (X=OH, I) crystals through replacement of the CO3 group with the NaO6 octahedron, which results in the crystal structural changes from P [ABSTRACT FROM AUTHOR]

Three alkaline metal borates Cs2B7O9(OH)5, K2B4O5(OH)4·H2O, and K2B4O5(OH)4·3.6H2O have been synthesized by a hydrothermal method. They were structurally characterized by single crystal X-ray diffraction. In the three compounds, the B–O anionic groups are all isolated, which are combined through the Cs/K–O polyhedra to form a three-dimensional (3D) network. The cationic framework presents different dimensions in Cs2B7O9(OH)5, K2B4O5(OH)4·H2O and K2B4O5(OH)4·3.6H2O. For Cs2B7O9(OH)5, which has been reported before, we obtained its large-scale crystal and the UV-vis diffuse reflectance spectral data of Cs2B7O9(OH)5 indicate that it has a UV cut-off edge of 209 nm which corresponds to an energy gap of 5.93 eV. Theoretical calculations were carried out to evaluate the band gaps of the title compounds, which illuminate that the replacement of K enlarges the band gap. Besides, the structural discrepancy among Cs2B7O9(OH)5, K2B4O5(OH)4·H2O and K2B4O5(OH)4·3.6H2O is compared to analyze the effect of the cation number on the polymerization degree of the B–O anionic groups. Density functional theory calculations were employed to evaluate the band structures and the density of states suggest that Cs2B7O9(OH)5 and K2B4O5(OH)4·H2O possess wide band gaps of 5.23 and 5.24 eV, respectively. Meanwhile, the large-scale crystal of Cs2B7O9(OH)5 was obtained. [ABSTRACT FROM AUTHOR]

Herein, a sodium magnesium diphosphate, Na7Mg4.5(P2O7)4, was synthesized via a standard solid-state reaction method, and a single crystal X-ray diffraction method was adopted to determine its crystal structure. It was found that it crystallizes in the triclinic system with the space group P1̅. The crystal structure of Na7Mg4.5(P2O7)4 features a parallelogram channel composed of corner/edge-sharing isolated [P2O7] dimers and a Na(2)O5 polyhedra to form a 3D framework. Thermal behaviors indicate that Na7Mg4.5(P2O7)4 congruently melts and IR spectrum shows the existence of the P2O7 groups. Moreover, Na7Mg4.5(P2O7)4 possesses an experimental band gap of 5.90 eV and an ultraviolet (UV) cut-off edge of about 210 nm, which was confirmed via diffuse reflection spectrum. To analyze the contribution of the atomic orbitals to the energy band, band structures and partial density of states (PDOS) of Na7Mg4.5(P2O7)4 have also been reported. [ABSTRACT FROM AUTHOR]

A series of phosphates, Pb9−xBax[Li2(P2O7)2(P4O13)2] (x = 0, 2, 6, 7), have been synthesized by a high temperature solution method and the crystal structures were determined by single crystal X-ray diffraction. They are isostructural and crystallize in the triclinic space group P1̅. It is interesting that there are two kinds of isolated polyphosphate anionic groups coexisting in the crystal structure, which is rare among phosphates. Their structures exhibit zero-dimensional [Li2(P2O7)2(P4O13)2]18− anionic clusters constructed by the LiO4, P2O7 and P4O13 groups, which are separated by the Pb2+ or Ba2+ cations. The structure of Pb9[Li2(P2O7)2(P4O13)2] could be obtained using Li2O as a dimensional reduction agent to dismantle Pb3P4O13. In addition, the infrared spectra and the UV-Vis-NIR diffuse reflectance spectra, as well as thermal analyses are reported. The first-principles theoretical studies are also carried out to understand the relationship between their electronic structures and linear optical properties. [ABSTRACT FROM AUTHOR]

Pb2Bi2GaB3O11, a new congruent-melting galloborate, which simultaneously contains two types of lone-pair cations and a π-conjugated system in one crystal structure, has been discovered through spontaneous crystallization. Single-crystal X-ray structural analysis shows that Pb2Bi2GaB3O11 crystallizes in the monoclinic space group of C2/c. The parameters of the unit cell are a = 17.318(5) Å, b = 8.868(3) Å, c = 6.779(2) Å, β = 90.238(4)° and Z = 6. The structure of Pb2Bi2GaB3O11 features three kinds of tunnels, circled by cation polyhedra, in two of which isolated BO3 groups reside. However, the open Bi4O4 channel, as the third tunnel formed by the Bi–O polyhedra, is hollow. Pb2Bi2GaB3O11 possesses an experimental band gap of 4.43 eV and an ultraviolet (UV) cut-off edge of about 280 nm, which is proven by its diffuse reflection spectrum. Theoretical calculations have also been executed to evaluate its band structure, partial density of state (PDOS) and birefringence. The results indicate that the title compound possesses a direct band gap with a theoretical value of 3.48 eV, and even indicate that the Pb2+ and Bi3+ ions are stereochemically active and cooperate with the BO3 groups, which contributes to a moderate birefringence of about 0.07 at 589 nm for Pb2Bi2GaB3O11. [ABSTRACT FROM AUTHOR]

A congruent melting compound LiNaV2O6 has been synthesized by high-temperature solution reaction and it has been grown with sizes up to 11 × 6 × 2 mm3 by the top-seeded growth method for the first time. LiNaV2O6 crystallizes in the monoclinic system with space group C2/c, with a = 10.184(2) Å, b = 9.067(2) Å, c = 5.8324(11) Å, β = 108.965(14)°. UV–Vis–NIR diffuse reflectance spectrum of LiNaV2O6 shows that it has a wide transmittance range from 385 to 2500 nm. The ab initio calculations show that the birefringence of LiNaV2O6 is 0.136 at 589.3 nm. Therefore, LiNaV2O6 may be a new birefringent material. Based on the analysis of the relationship between crystal structure and linear optical properties, it is found that the large birefringence is attributed to the particular arrangement of V–O anionic groups. [ABSTRACT FROM PUBLISHER]

Three new carbonate halides, Cs3Pb2(CO3)3I, KBa2(CO3)2F and RbBa2(CO3)2F have been synthesized with hydrothermal and solid-state methods. Cs3Pb2(CO3)3I is the first product in the lead carbonate iodides family; KBa2(CO3)2F and RbBa2(CO3)2F are the first two centrosymmetric compounds found in the alkaline-alkaline earth carbonate fluorides family. Cs3Pb2(CO3)3I crystallizes in a centrosymmetric space group C2/ m, and exhibits a two- dimensional layered structure which is formed by [Cs4Pb4(CO3)6I2]∞ double-layers consisting of [Pb2(CO3)3I]∞ single-layers bridged by the Cs atoms. KBa2(CO3)2F and RbBa2(CO3)2F, which are isostructural, crystallize in a trigonal crystal system with a centric space group of R featuring a honeycomb-like framework. First principle calculations indicate that Cs3Pb2(CO3)3I has a moderate birefringence and explain the difference between the band gaps of the title compounds from electron structures. The effects of cations and halogens on the structures and properties of the title compounds are also discussed. [ABSTRACT FROM AUTHOR]

Two magnesium silicate fluorides, Mg5(SiO4)2F2 (compound 1) and Mg3SiO4F2 (compound 2), have been successfully synthesized by solid-state reactions for the first time. Compound 1 crystallizes in the space group P21/c (no. 14) of the monoclinic system, whereas the latter belongs to the space group Pnma (no. 62) of the orthorhombic system. As for the crystal structure, compound 1 can be described on the basis of a “framework” made by Mg1O4F2 and Mg2O5F octahedra forming many rings, in which the Mg3 and Si atoms reside. Compound 2 can also be described as the rings created by Mg2O4F2 octahedra, in which the Mg1 and Si atoms reside. Thermal analysis and the infrared spectrum of compound 1 were measured. In addition, the UV-Vis-NIR diffuse-reflectance spectrum exhibits that the relatively wide band gap is about 5.32 eV for compound 1, which is consistent with the theoretical value. The band structure and linear optical properties of title compounds are also theoretically calculated. [ABSTRACT FROM AUTHOR]

A noncentrosymmetric aluminum borate crystal, Al5BO9, was obtained via high-temperature solution method. Considering the structure diversities of Al5BO9, the single crystal structure was cautiously redetermined before the investigation. The fundamental building blocks of the structure are BO3 triangles, AlO4 tetrahedra, and AlO6 octahedra. Since Al5BO9 only consists of strong covalent B–O and Al–O bonds, it is worth investigating the structure–optical property relationship thoroughly, especially the linear and nonlinear optical properties. To gain further insight into the origin of the nonlinear optical response of Al5BO9, the electronic structure calculations, second harmonic generation (SHG)-weighted electron density, and dipole moment of polyhedra were analyzed in detail. All evidences deduced from calculated results indicate that the SHG contribution from the Al–O polyhedra is more pronounced than that of the BO3 group in Al5BO9, which is anticipated to open a window for the search and design of new inorganic materials. [ABSTRACT FROM AUTHOR]

The apatite-type strontium vanadate fluoride Sr5(VO4)3F was synthesized by standard solid-state reaction method and grown by spontaneous crystallization flux method. It crystallizes in the hexagonal space group P63/ m with lattice constants a = 9.988(4) Å, c = 7.415(6) Å, Z = 2. The structure consists of infinite three-dimensional [Sr(2)2(VO4)3]5+ framework with tunnels along the c axis, where Sr(1)2+ and F- ions are filled. Functional groups in the structure have been identified by IR spectroscopy and the very high thermal stability up to 1400 °C has been identified by TG and DSC analyses. UV/Vis/NIR diffuse reflectance spectroscopy and first-principle theoretical studies were also carried out to aid the understanding of optical properties and electronic structure. [ABSTRACT FROM AUTHOR]

Single crystals of PbGa 2 Q 4 (Q = S, Se) have been successfully synthesized by solid-state reactions and their structures are determined by single-crystal X-ray diffraction methods. They are isostructural and crystallize in the orthorhombic space group Fddd ( Z = 32). In their crystal structures, the GaS 4 or GaSe 4 units are connected with corner or edges sharing to form layers, and these layers are bridged by Pb atoms to generate a three-dimensional (3D) framework. The UV–Vis–IR diffuse reflectance spectra exhibit that the optical band gaps are about 2.38 and 1.83 eV for PbGa 2 S 4 and PbGa 2 Se 4 , respectively, which are consistent with the calculated values. Their thermal behaviors and Raman spectra were also measured. First-principle theoretical studies are used to aid the understanding of electronic structures and linear optical properties. [ABSTRACT FROM AUTHOR]

Two novel isomorphic borates, Q18Mg6(B5O10)3(B7O14)2F (Q=Rb and Cs), were synthesized from high-temperature solutions. These borates are created from two kinds of isolated polyborate anionic groups, [B5O10] and [B7O14], and are further examples of two kinds of isolated polyborate anions coexisting in one borate structure. Although the title compounds are new structures, they are similar to the structures of the KBe2BO3F2 (KBBF) series of compounds, for example, Na2Be4B4O11 and γ-KBe2B3O7, which can be regarded as the substitution of [BO3] and [B2O5]/[B3O6] groups with [B7O14] and [B5O10] groups, respectively. It is found that the coexisting BO groups tend to have similar structures. Also, the isolation of [B5O10] and [B7O14] in the title compounds mainly derives from the special role of magnesium tetrahedra, which has a similar role to that of the BeO4 tetrahedra in the KBBF series compounds. Electron-density maps and bond-overlap population (BOP) were calculated to illustrate this feature. [ABSTRACT FROM AUTHOR]

The magnesium borate fluoride Mg5(BO3)3F was grown by spontaneous crystallization with molten flux based on the MgF2-LiF-Na2CO3-H3BO3 solvent. Structure solution from single-crystal X-ray diffraction shows that the title compound crystallizes in the orthorhombic space group Pnma (No. 62) with cell dimensions of a = 10.068(5) Å, b = 14.858(7) Å, c = 4.540(2) Å and Z = 4. Its structure features a three-dimensional (3D) Mg-O-F framework composed of MgO5F and MgO6 polyhedra and isolated BO3 groups. The detailed structure comparison referred to Mg5(BO3)3F, Mg3BO3F3 and β-Mg2BO3F was carried out. The infrared spectrum (IR) and the bond valence sum (BVS) calculations of Mg5(BO3)3F verify the validity of the structure. The calculated band structure and the density of states of Mg5(BO3)3F suggest that its indirect bandgap is 5.27 eV. The compound was additionally investigated by UV/Vis-NIR diffuse reflectance spectroscopy and thermal analysis. [ABSTRACT FROM AUTHOR]

The organic-inorganic hybrid nonlinear optical (NLO) material NH4B( d-(+)-C4H4O5)2 ·H2O (NBC) was synthesized in a borate-carboxylic acid system. Its structure was determined by single crystal X-ray diffraction. It crystallizes in the orthorhombic system, space group Pna21 (No. 33), with cell parameters a = 11.484(6) Å, b = 5.354(3) Å, c = 21.079(12) Å, V = 1296.0(12), Z = 4. It exhibits a three-dimensional pseudo tunnel structure consisting of fundamental building block [B( d-(+)-C4H4O5)2]- anions. The small cavities are occupied by the H2O molecules and NH4+ cations, which stabilize the whole structure by O-H ···O and N-H ···O hydrogen bonds. The powder X-ray diffraction (PXRD) of the crystal was also recorded. Elemental analyses, FT-IR and FT-Raman spectra analyses, thermal analysis, and diffuse-reflectance spectra for the compound are also presented, as are band structures and density of states calculation. Nonlinear optical measurements indicate that the material has second harmonic generation (SHG) properties and is phase-matchable. [ABSTRACT FROM AUTHOR]

Highlights: [•] A new potassium lead pentaborate, KPbB5O9, has been synthesized. [•] Infrared spectrum has been used to verify the validity of the structures. [•] KPbB5O9 has an UV cut off edge at about 230nm. [•] The calculated band structures suggest that the direct gap of KPbB5O9 is 3.781eV. [ABSTRACT FROM AUTHOR]

Highlights: [•] A new compound, K2Bi(IO3)4Cl, is obtained from the KIO3–BiCl3 system. [•] It crystallizes in the monoclinic system, space group P21/c. [•] Its structure consists of iodide-linked infinite ∞[Bi(IO3)4] layer. [•] Thermal analysis indicated four weight losses occurred between 398°C and 805°C. [ABSTRACT FROM AUTHOR]

Highlights: [•] A new bromoborate Na3B6O10Br has been synthesized in M–B–O–X (M: alkali metals; X: halogen) system. [•] Na3B6O10Br was grown by high temperature solution method since it melts incongruently. [•] Crystal structure of Na3B6O10Br is different from that of K3B6O10Br. [•] Electronic structures and optical properties of Na3B6O10Br were studied. [Copyright &y& Elsevier]

Two new ternary borates, Rb3MB5O10 (M = Zn, Cd) have been synthesized by solid-state reactions, and their structures were determined by single-crystal X-ray diffraction. They crystallize in the same monoclinic space group P21/n with lattice constants a = 10.449(11) A˚ , b = 9.414(10) A˚ , c = 11.690(12) A˚ , and b = 105.888(11)º for Rb3ZnB5O10, while a = 7.6391(5)A˚ , b =19.2304(13)A˚ , c = 7.6905(5)A˚ , and β = 116.698(4)º for Rb3CdB5O10. And their crystal structures both contain the interesting two-dimension (2D) infinite [MB5O10]1∞ (M = Zn, Cd) layers. However, owing to the different configurations and stacking directions of the [MB5O10]1∞ (M = Zn, Cd) layers, Rb3ZnB5O10 and Rb3CdB5O10 are not isostructural. The IR spectra further confirm the presence of both BO3 and BO4 groups and UV-Vis-NIR diffuse reflectance spectra show their band gaps are 2.66 and 2.34 eV for Rb3ZnB5O10 and Rb3CdB5O10, respectively. [ABSTRACT FROM AUTHOR]

Two similarly stoichiometric boratehalides, NaBa4(AlB4O9)2Br3and NaBa4(B5O9)2F2Cl, have been successfully designedand synthesized, and their structures were determined by single-crystalX-ray diffraction. Their crystal structures feature the [AlB4O9]∞and [B5O9]∞networks, respectively. NaBa4(AlB4O9)2Br3is noncentrosymmetricand crystallizes in polar space group P42nm, while NaBa4(B5O9)2F2Cl is centrosymmetric and crystallizesin monoclinic space group P21/n. Powder second-harmonic generation (SHG) measurementsreveal that NaBa4(AlB4O9)2Br3has an optical nonlinearity comparable to that ofKH2PO4(KDP) and is type I phase-matchable.In addition, infrared and UV–Vis–NIR diffuse reflectancespectroscopy, as well as electronic band structure calculations, wereperformed on the reported materials. [ABSTRACT FROM AUTHOR]

Abstract: A series of lead-containing halogen oxyborates, Pb6B3O10 X (X=F, Cl, Br), have been grown by high-temperature solution method and their crystal structures were determined by single-crystal X-ray diffraction. They are isostructural and crystallize in the space group Pbcm of the orthorhombic crystal system. The crystal structures are dominated by one-dimensional ∞[(Pb4O)(BO3)3] “Zig-Zag”-chains, while the remaining Pb atoms and X (X=F, Cl, Br) atoms are filled to balance the charge. Compared with the previously reported compound Pb4O(BO3)2 (the molecular formula Pb4O(BO3)2 can be regarded as Pb6B3O10.5) with the space group Aba2, the structures of Pb6B3O10 X (X=F, Cl, Br) are completely different from that of Pb4O(BO3)2. IR spectroscopy, UV–vis-NIR diffuse reflectance spectroscopy, thermal analysis, and theoretical calculations were also performed on the reported materials. [Copyright &y& Elsevier]

Borate not graphene: The [B6O12]∞6− single borate layer is a graphene‐like layer (see figure). The weak Na+Br(Cl)− ionic connection between the layers leads to the layer cleavage, and difficulty of the block crystal growth. [ABSTRACT FROM AUTHOR]

Highlights: [•] A new lithium dilead pentaborate, LiPb2B5O10, has been synthesized. [•] LiPb2B5O10 is a congruent melting compound. [•] The band gap calculation of LiPb2B5O10 revealed an indirect gap with 3.433eV. [Copyright &y& Elsevier]

The aluminosilicate Li2Na3AlSi2O8 was crystallized from the Li2CO3-H3BO3 flux system. It crystallizes in the orthorhombic space group Cmca, with cell dimensions a = 14.1045 (19) Å, b = 14.7054 (19) Å, c = 7.0635 (9) Å, and Z = 8. The crystal structure consists of a two-dimensional infinite layer, which is composed of [Al2Si2O12] groups and [SiO4] tetrahedra. The lithium and sodium atoms filling in the interlayer and intralayer link the layers together and balance the charge. IR spectroscopy and BVS calculations were used to verify the validity of the structure. The calculated band structures and the density of states of Li2Na3AlSi2O8 suggest that its direct gap is 4.28 eV. [ABSTRACT FROM AUTHOR]

The aluminosilicate Li2Na3AlSi2O8 was crystallized from the Li2CO3-H3BO3 flux system. It crystallizes in the orthorhombic space group Cmca, with cell dimensions a = 14.1045 (19) Å, b = 14.7054 (19) Å, c = 7.0635 (9) Å, and Z = 8. The crystal structure consists of a two-dimensional infinite layer, which is composed of [Al2Si2O12] groups and [SiO4] tetrahedra. The lithium and sodium atoms filling in the interlayer and intralayer link the layers together and balance the charge. IR spectroscopy and BVS calculations were used to verify the validity of the structure. The calculated band structures and the density of states of Li2Na3AlSi2O8 suggest that its direct gap is 4.28 eV. [ABSTRACT FROM AUTHOR]