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Trigonal planar units with large polarizability anisotropy and high physicochemical stability are ideal structural units for exploring nonlinear optical (NLO) materials. Integrating the merits of two types of triangular‐like moieties, a family of second‐order NLO‐active hybrid halides, MATX (X = Cl (1), Br (2), and I (3)), are achieved. MATX crystallizes in a nonpolar space group of P6¯$P\overline 6 $2c but exhibits the optimal spatial arrangement and superior NLO performance. The low coordination planar trigonal AgX3 units enable segregation in layers of the three‐winged propeller‐like Me3TPA units. All of the layers are packed in a perfect parallel fashion, making the functional materials exhibit superior NLO performances, including the phase matchable behavior with strong SHG responses (6.2/1, 6.5/2, and 7.6/3 times that of potassium dihydrogen phosphate), large birefringence (0.232/1, 0.252/2 and 0.260/3 at 1064 nm), high laser damage threshold, wide transparent window, and easiness of crystal growth. The first‐principles calculations reveal that the coexistence of strong linear and nonlinear optical properties are ascribed to the synergistic effect of the trigonal moieties. This study points out a useful path for the rational design of excellent NLO materials. [ABSTRACT FROM AUTHOR]

Through systematic experiments, two novel mercury iodate sulfates, namely, Hg2(IO3)2(SO4)(H2O) and Hg2(IO3)2(SO4) were obtained. They crystallize in monoclinic space group C2 and C2/c, respectively. Hg2(IO3)2(SO4)(H2O) exhibits the [Hg(IO3)]+ polar cationic layer inherited from Hg(IO3)2 and the three‐dimensional (3D) framework inherited from HgSO4. This enables Hg2(IO3)2(SO4)(H2O) to generate a strong second harmonic generation (SHG) response of 6 times that of KH2PO4 (KDP). The structure of Hg2(IO3)2(SO4) is very similar to that of Hg2(IO3)2(SO4)(H2O), and they can be transformed into each other. Hg2(IO3)2(SO4)(H2O) shows a large optical band gap of 3.98 eV and a high dehydration temperature of 250 °C. This study indicates that by reasonable design, the introduction of multiple functional groups into a compound may combine their advantages to achieve good overall optical performance. [ABSTRACT FROM AUTHOR]

An organic–inorganic hybrid polyiodate, namely, [o‐C5H4NHOH]2[I7O18(OH)]⋅3 H2O (I), featuring a novel branched polyiodate chain has been obtained by evaporation method. [o‐C5H4NHOH]2[I7O18(OH)]⋅3 H2O (I) crystalizes in the polar space group Ia and features an [I7O18(OH)]∞2- branched polyiodate chain in which [I3O9]3− trimers are grafted on the same side of the one‐dimensional (1D) chain based on [I4O11(OH)]3− tetramers. The asymmetric organic amine groups are beneficial to the polymerization of iodate groups and inducing the formation of the non‐centrosymmetric (NCS) structure. Compound I exhibits a rather large Second‐Harmonic‐ Generation (SHG) signal of 8.5×KH2PO4 (KDP) upon 1064 nm laser radiation, a moderate band gap of 3.90 eV and a high laser‐induced‐damage‐threshold (LIDT) of 182.34 MW cm−2, hence it is a promising new SHG material. The relationship between the structures of the organic amine groups and the overall structures has been also analyzed. [ABSTRACT FROM AUTHOR]

The first alkali‐metal vanadium iodate fluoride, CsVO2F(IO3), with a novel 3D anionic framework, has been rationally designed and hydrothermally synthesized. The 3D [VO2F(IO3)]− framework in CsVO2F(IO3) is built from 0D Λ‐shaped cis‐[VO3F(IO3)2]4− polyanions via corner‐sharing of oxo anions and bridging of the iodate groups. CsVO2F(IO3) displays both a strong second‐harmonic generation (SHG) 1.1 times as strong as KTiOPO4 (KTP) under 2.05 μm laser radiation and high laser‐induced damage threshold (LIDT) of 107.9 MW cm−2. This work provides a new route to design SHG crystals with stable 3D anionic structures from low‐dimensional structural building units. [ABSTRACT FROM AUTHOR]

A large nonlinear optical (NLO) coefficient and a wide band gap are two crucial but contradictory parameters that are difficult to achieve simultaneously in a single infrared (IR) NLO compound. A salt‐inclusion chalcogenide (SIC), Li[LiCs2Cl][Ga3S6] (1), was prepared that presents a nanosized tunnel framework constructed from monotype chalcogenide tetrahedra. Highly oriented covalent GaS4 tetrahedra in the host lead to a moderate second harmonic generation response (0.7 AgGaS2), and ionic guests effectively broaden the band gap to the widest value (4.18 eV) among all IR NLO chalcogenides, thereby achieving a remarkable balance between NLO efficiency and band gap. [ABSTRACT FROM AUTHOR]

To develop new mid-infrared (MIR) nonlinear optical (NLO) materials, which can overcome the low laser damage threshold (LDT) of the commercial MIR-NLO crystals (AgGaS2, AgGaSe2 and ZnGeP2) and simultaneously keep the large NLO susceptibility, is necessary for high-power MIR laser frequency conversion technology. To improve the LDT, a new strategy of increasing lattice stability was adopted. Here, the strongly covalent structural unit of the PS4 tetrahedron was introduced into AgGaS2 (AGS), and that led to the isolation of the first compound in AgI-GaIII-PV-S system, namely, AgGa2PS6 ( Cc). It retains a large SHG efficiency (1.0×AGS) with phase-matchable ability, and also exhibits an improved LDT (5.1×AGS), indicating AgGa2PS6 is a new promising MIR-NLO crystal. Moreover, a novel 3D framework of [Ga2PS6]−, with triangular-shaped channels, as well as interesting single triangular geometry of AgS3-both of which are very rare in reported sulfides-was discovered in AgGa2PS6. Furthermore, theoretical calculations, and lattice energy and thermal expansions analyses suggest that the PS4 group makes a large contribution to the large SHG efficiency and high LDT. [ABSTRACT FROM AUTHOR]

Two new polar potassium gold iodates, namely, K2Au(IO3)5 ( Cmc21) and β-KAu(IO3)4 ( C2), have been synthesized and structurally characterized. Both compounds feature zero-dimensional polar [Au(IO3)4]− units composed of an AuO4 square-planar unit coordinated by four IO3− ions in a monodentate fashion. In β-KAu(IO3)4, isolated [Au(IO3)4]− ions are separated by K+ ions, whereas in K2Au(IO3)5, isolated [Au(IO3)4]− ions and non-coordinated IO3− units are separated by K+ ions. Both compounds are thermally stable up to 400 °C and exhibit high transmittance in the NIR region ( λ=800-2500 nm) with measured optical band gaps of 2.65 eV for K2Au(IO3)5 and 2.75 eV for β-KAu(IO3)4. Powder second-harmonic generation measurements by using λ=2.05 μm laser radiation indicate that K2Au(IO3)5 and β-KAu(IO3)4 are both phase-matchable materials with strong SHG responses of approximately 1.0 and 1.3 times that of KTiOPO4, respectively. Theoretical calculations based on DFT methods confirm that such strong SHG responses originate from a synergistic effect of the AuO4 and IO3 units. [ABSTRACT FROM AUTHOR]

The new compounds Ba3(BS3)1.5(MS3)0.5 (I) with M: Sb, Bi and Ba3(BQ3)(SbQ3) (II) with Q: S, Se are synthesized by solid state reaction of stoichiometric mixtures of the elements (graphite crucible in an evacuated silica tube, 820-920 °C). [ABSTRACT FROM AUTHOR]