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Benefiting from the planar π-conjugated (HxC3N3O3)x−3 (x = 0–3) groups, cyanurate crystals have recently become a research hotspot in birefringent materials. Herein, by combining the (HxC3N3O3)x−3 (x = 0–3) group with the (CN3H6)+ cationic group, two metal-free cyanurates, GU(H2C3N3O3) (I) and GU3(H2C3N3O3)3(H3C3N3O3) (II), were obtained by the hydrothermal method. These compounds have wide band gaps (∼5 eV) and a large birefringence (∼0.40@400 nm), demonstrating their potential to be ultraviolet birefringent crystals. Moreover, first-principles calculations indicate that their large birefringence values originated from the synergistic effect of the (CN3H6)+ cations and (HxC3N3O3)x−3 (x = 0–3) groups. These findings provide a new design strategy for exploring low-cost UV birefringent crystals with a large birefringence. [ABSTRACT FROM AUTHOR]

Deep‐ultraviolet (DUV) nonlinear optical (NLO) crystals are vital to the development of science and state‐of‐the‐art technologies, but the exploration of these important optoelectronic materials is hindered by the contradiction between NLO effect and energy band gap as well as the sensitivity of DUV phase‐matching to optical birefringence. Here, in order to achieve a well balanced DUV NLO performance, we chose the diamond‐like structure as the prototype template for the material design and synthesized the first DUV NLO hydroxycarbonate crystal, LiZn(OH)CO3. This compound simultaneously has a wide band gap (>6.53 eV), a strong second harmonic generation response (ca. 3.2×KDP), and a large birefringence (0.147 at 1064 nm) with the shortest DUV phase‐matching capability (λPM<190 nm) among all reported NLO carbonates. Moreover, the structure–property relationships in LiZn(OH)CO3 are analyzed by first‐principles calculations. This work presents an effective design strategy to push the NLO performance of hydroxycarbonates into the DUV region. [ABSTRACT FROM AUTHOR]

A new ternary selenostannate Ba6Sn6Se13 has been synthesized by a high temperature solid-state method. The compound crystallizes in the non-centrosymmetric orthorhombic space group P212121 and may be represented as Ba6Sn52+Sn4+Se13 with mixed valence Sn atoms. Sn4+ cations lie in a tetrahedral environment, while Sn2+ cations are found in two kinds of coordination environments: the trigonal pyramid and quadrangular pyramid. SnSen (n = 3, 4, 5) polyhedra are further connected to generate a three-dimensional framework with Ba2+ residing in cavities. Ba6Sn6Se13 shows moderate nonlinear optical response and is the first reported NLO compound in the Ba–Sn–Se system. In addition, diffuse reflectance spectroscopy measurement indicates that the band gap of Ba6Sn6Se13 is 1.52(2) eV and thermal analysis suggests that the compound melts incongruently. The theoretically calculated SHG response and band gap are in good agreement with experimental results. [ABSTRACT FROM AUTHOR]

A new ternary phosphidopolysilicate (IV), KSi2P3, has been synthesized by high temperature solid state reaction. The compound crystallizes in a new structure type in the monoclinic space group C2/c with a=10.1327(5)Å, b=10.1382(5)Å, c=21.1181(10)Å, β=96.88(0)°, and Z=8. In the structure, all SiP4 tetrahedra are connected with each other by corner-sharing P atoms to form layers, which are stacked along c direction and separated by K+ cations. The two-dimensional structure of KSi2P3 contrasts with those of the two known members in the ternary A/Si/P (A=alkali metal) system, namely Na5SiP3 (zero-dimensional) and K2SiP2 (one-dimensional), which contains less amount of Si. The band gap deduced from UV–vis–IR diffuse reflectance spectrum is 1.72eV. [ABSTRACT FROM AUTHOR]

We identify the microscopic structural origins determining the bandgaps in the deep-ultraviolet borates, and propose an efficient method for the prediction of their bandgaps. This method considers only the chemical bond lengths around oxygen atoms and achieves the very high precision with the relative error <5% typically. Its validity is verified by the first-principles studies, which reveal the strong dependence of bandgaps on the coordination environment around oxygen atoms. Our studies have great implications on the search and design of optoelectronic functional materials with large bandgap. [ABSTRACT FROM AUTHOR]

Abstract: The predictive capabilities of the density functional theory with various exchange–correlation functionals on the energy band gaps and optical properties in ultraviolet nonlinear optical (UV NLO) crystals are systematically investigated. We find that the energy band gaps of these crystals can be accurately predicted by the non-local hybrid functionals and sX-LDA functionals, but their calculated optical properties are not consistent with the experimental results compared to the usually adopted LDA or GGA functionals with the scissors corrections. Accordingly, we propose that a precise and effective strategy to study the optical properties in the UV NLO crystals without any experimental parameter should be the combination of different functional calculations. [Copyright &y& Elsevier]

[Display omitted] • Recent developments in mid-IR NLO materials utilizing f 0 rare earth chalcogenides (RE = Sc, Y, La) are reviewed. • The advantages of utilizing f 0 rare earth chalcogenides as mid-IR NLO materials are thoroughly analyzed. • Several useful conclusions and considerations for future research are presented. Mid-infrared (mid-IR) nonlinear optical (NLO) materials are extensively researched as a vital optoelectronic material family with widespread applications ranging from civil to military fields. Metal chalcogenides possess a wide range of IR transparency and vast structural diversity, making them ideal system for exploration of novel mid-IR NLO materials. Incorporating rare earth elements with 4 f 0 and 5 f 0 electrons, including Sc, Y, and La, into chalcogenide structures in mid-IR NLO materials has been actively studied in the recent years. In this review, we categorize all typical f 0 rare earth (RE = Sc, Y, La) chalcogenides in the inorganic crystal structure database based on their NLO functional groups. We then assess their energy band gaps, NLO coefficients, birefringence, IR cut-offs, and mechanical properties using available experimental data and first-principles results and investigate the correlation between structural features and mid-IR NLO performance. It is showed that the f 0 rare earth chalcogenides can possess suitable birefringence and NLO response for mid-IR NLO applications, while not compromising energy band gap, thus may have a well-balanced mid-IR NLO performance. The prospects of novel f 0 rare earth chalcogenides with favorable mid-IR NLO performance are also discussed. [ABSTRACT FROM AUTHOR]