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One 3d-metal coordination polymer [Zn(Hspas)(Hpco)(H2O)]n (1) (NaH2spas = 5-sulfoisophthalic acid monosodium salt, Hpco = 2-pyridinecarbaldehyde oxime), was synthesized by solvent evaporation method under magnetci field. Each Zn atom is hexcoordinated with a distorted octahedral arrangement. Each Hspas2– anion acts as a tridentate ligand, which bridges with three Zn ions to form a two-dimensional layered structure. The two-dimensional structures are further linked by hydrogen bonds to generate a three-dimensional supramolecular structure. Complex 1 exhibits the photoluminescent emission with maximum at 396 nm, which arises from the ligand centered π–π*-transitions. The emission intensity of complex 1 is higher than that of NaH2spas ligand, which is indicative of the influence of the d10 closed shell electronic configuration of zinc ion on fluorescence property. In addition, complex 1 has the response of second-harmonic-generation (SHG) with 2 times that of KH2PO4. [ABSTRACT FROM AUTHOR]

Poisson's ratio in chiral Cosserat elastic solids is considered. Chirality allows the Poisson's ratio to exceed classical bounds, even if the material is directionally isotropic and all elastic moduli are within thermodynamic limits based on strain energy density. Poisson's ratio in chiral rods depends on the chiral elastic constants as well as on the shear and bulk moduli, assumed positive. Poisson's ratio can be greater than 0.5 or smaller than −1 for slender chiral specimens. [ABSTRACT FROM AUTHOR]

Polar magnetic materials exhibiting appreciable asymmetric exchange interactions can potentially host new topological states of matter such as vortex-like spin textures; however, realizations have been mostly limited to half-integer spins due to rare numbers of integer spin systems with broken spatial inversion lattice symmetries. Here, we studied the structure and magnetic properties of the S = 1 integer spin polar magnet β-Ni(IO3)2 (Ni2+, d8, 3F). We synthesized single crystals and bulk polycrystalline samples of β-Ni(IO3)2 by combining low-temperature chemistry techniques and thermal analysis and characterized its crystal structure and physical properties. Single crystal X-ray and powder X-ray diffraction measurements demonstrated that β-Ni(IO3)2 crystallizes in the noncentrosymmetric polar monoclinic structure with space group P21. The combination of the macroscopic electric polarization driven by the coalignment of the (IO3)− trigonal pyramids along the b axis and the S = 1 state of the Ni2+ cation was chosen to investigate integer spin and lattice dynamics in magnetism. The effective magnetic moment of Ni2+ was extracted from magnetization measurements to be 3.2(1) µB, confirming the S = 1 integer spin state of Ni2+ with some orbital contribution. β-Ni(IO3)2 undergoes a magnetic ordering at T = 3 K at a low magnetic field, μ0H = 0.1 T; the phase transition, nevertheless, is suppressed at a higher field, μ0H = 3 T. An anomaly resembling a phase transition is observed at T ≈ 2.7 K in the Cp/T vs. T plot, which is the approximate temperature of the magnetic phase transition of the material, indicating that the transition is magnetically driven. This work offers a useful route for exploring integer spin noncentrosymmetric materials, broadening the phase space of polar magnet candidates, which can harbor new topological spin physics.

The noncentrosymmetric structure is one prerequisite of a nonlinear optical (NLO) material. Here, a sulfate Cs2Ca2(SO4)3 with a noncentrosymmetric structure was synthesized by high‐temperature solid‐state reaction, and its crystals were grown by spontaneous crystallization. Single‐crystal X‐ray diffraction indicates that Cs2Ca2(SO4)3 features a three‐dimensional framework constituted by corner‐sharing CaO6 octahedra and SO4 tetrahedra. Optical characterizations suggest that Cs2Ca2(SO4)3 is transparent down to 200 nm and exhibits a moderate second‐order NLO response of about 0.6 × KH2PO4. Electronic band structure calculations were performed to elucidate the optical origin. Furthermore, the title compound has good thermal stability of up to about 1000 K, which is greatly higher than those of NLO sulfates reported recently. This work may shed useful light on the development of new NLO sulfates with high thermal stability. [ABSTRACT FROM AUTHOR]

The noncentrosymmetric structure is one prerequisite of a nonlinear optical (NLO) material. Here, a sulfate Cs2Ca2(SO4)3 with a noncentrosymmetric structure was synthesized by high‐temperature solid‐state reaction, and its crystals were grown by spontaneous crystallization. Single‐crystal X‐ray diffraction indicates that Cs2Ca2(SO4)3 features a three‐dimensional framework constituted by corner‐sharing CaO6 octahedra and SO4 tetrahedra. Optical characterizations suggest that Cs2Ca2(SO4)3 is transparent down to 200 nm and exhibits a moderate second‐order NLO response of about 0.6 × KH2PO4. Electronic band structure calculations were performed to elucidate the optical origin. Furthermore, the title compound has good thermal stability of up to about 1000 K, which is greatly higher than those of NLO sulfates reported recently. This work may shed useful light on the development of new NLO sulfates with high thermal stability. [ABSTRACT FROM AUTHOR]

With increasing research interests in the field of light-matter interactions, various methods have been developed for regulating nonlinear optical (NLO) materials. However, the design and synthesis of organic molecular materials for second-order nonlinear optics remain a great challenge because of the strict requirement of the materials to possess a noncentrosymmetric structure. In this work, two benzothiadiazole (BTD) derivatives referred to as BTD-H and BTD-F were synthesized, and their NLO properties in the crystalline states were studied. It was found that introducing fluorine into the BTD backbone effectively tuned the crystal packing styles of BTD derivatives to a noncentrosymmetric system for effective second-order NLO responses. Such a strategy to induce the noncentrosymmetric structure by introducing the fluorine atoms and halogen interactions may provide guidance for future engineering of organic NLO molecular materials. [ABSTRACT FROM AUTHOR]

In this work we investigate the properties of elastic waves propagating in gyroid lattices. First, we rigorously characterize the lattice from the point of view of crystallography. Second, we use Bloch–Floquet analysis to compute the dispersion relations for elastic waves. The results for very long wavelengths are then compared to those given by classic elasticity for a cubic material. A discrepancy is found in terms of the polarization of waves and it is related to the noncentrosymmetry of the gyroid. The gyroid lattice results to be acoustically active, meaning that transverse waves exhibit a circular polarization when they propagate along an axis of rotational symmetry. This phenomenon is present even for very long wavelengths and is not captured by classic elasticity.

Single crystals of Potassium Hydrogen Phthalate (KHP) have been grown from aqueous solution by slow evaporation technique at 37°C. The carbon and hydrogen environment in molecular design of KHP is determined by the FT-NMR method. The mechanical strength of KHP was investigated by Vickers microhardness test. The relative SHG efficiency of KHP was measured by employing Kurtz and Perry powder technique using a Q-switched mode-locked Nd:YAG laser emitting 1064 nm. The intensity of the green emission was found to be 1.12 times greater than KDP of KHP crystal. Third-order nonlinear optical properties were determined by the Z-scan procedure by He-Ne laser. Closed aperture Z-scan study reveals the positive nonlinearity in KHP and open aperture Z-scan demonstrates the nonlinear absorption is reverse saturation absorption. [ABSTRACT FROM AUTHOR]

The loss of centrosymmetry via oxygen octahedral rotations is demonstrated in the n = 2 Dion-Jacobson family of layered oxide perovskites, A′LaB2O7 (A′ = Rb, Cs; B = Nb, Ta). Ab initio density functional theory calculations predict that all four materials should adopt polar space groups, in contrast to the results of previous experimental studies that have assigned these materials to the centrosymmetric P4/ mmm space group. Optical second harmonic generation experiments confirm the presence of a noncentrosymmetric phase at ambient temperature. Piezoresponse force microscopy experiments also show that this phase is piezoelectric. To elucidate the symmetry-breaking and assign the appropriate space groups, the crystal structure of CsLaNb2O7 is refined as a function of temperature from synchrotron X-ray diffraction data. Above 550 K, CsLaNb2O7 adopts the previously determined centrosymmetric P4/ mmm space group. Between 550 and 350 K, the symmetry is lowered to the noncentrosymmetric space group A mm2. Below 350 K, additional symmetry lowering is observed as peak splitting, but the space group cannot be unambiguously identified. [ABSTRACT FROM AUTHOR]

Two quaternary sulfides RE 3 Sb 0.33 SiS 7 ( RE =La, Pr) have been prepared from stoichiometric mixtures of elements at 1223 K in an evacuated silica tube. They are the first examples of chalcogenides in the quaternary RE /Si/Sb/ Q (RE=rare earth metal; Q =S, Se, Te) system. These two isostructural materials crystallize in the Ce 3 Al 1.67 S 7 structure type in the hexagonal space group P 6 3 . Their structure features one-dimensional chains of face-sharing SbS 6 octahedra running parallel to the c direction surrounded by the discrete SiS 4 tetrahedra and RE cations. The La 3 Sb 0.33 SiS 7 exhibits a SHG signal about 0.5 times that of the commercially used IR NLO material AgGaS 2 at 2.05 μm laser. The optical gap of 1.92 eV for La 3 Sb 0.33 SiS 7 was deduced from UV/Vis reflectance spectroscopy. [ABSTRACT FROM AUTHOR]

A series of noncentrosymmetric sulfides Ln8Sb2S15 (Ln = La, Pr, Nd) were prepared from stoichiometric mixtures of the elements at 1223 K in an evacuated silica tube. The compounds Ln8Sb2S15 with Ln = La and Nd are isostructural to Pr8Sb2S15 and crystallize in the tetragonal noncentrosymmetric space group I41cd. Their structure contains discrete [SbS3]3- trigonal pyramids separated by Ln3+ cations and S2- anions. La8Sb2S15 shows second harmonic generation with intensities 1.2 times that of the commercially used IR NLO (nonlinear optics) material AgGaS2 (at 2.05 μm laser). It exhibits excellent thermal stability up to 663 °C. Studies with UV/Vis-NIR diffuse reflectance spectroscopy show that La8Sb2S15 has an optical gap of around 2.3 eV, and a DFT study indicates a direct band gap with an electronic transfer excitation of S 3p electrons to a La 5d orbital. [ABSTRACT FROM AUTHOR]

Herein, we investigate human single hydroxyapatite crystals (enamel and dentine) by convergent-beam electron diffraction (CBED) and automated electron-diffraction tomography (ADT). The CBED pattern shows the absence of the mirror plane perpendicular to the c axis leading to the P63 space group instead of the P63/ m space group considered for larger-scale crystals, this is confirmed by ADT. This experimental evidence is of prime importance for understanding the morphogenesis and the architectural organization of calcified tissues. [ABSTRACT FROM AUTHOR]

The noncentrosymmetric borate CsCdBO3 was synthesized by a solid-state reaction, and its structure was determined by single-crystal X-ray diffraction. The crystal structure is a complicated three-dimensional network composed of CdO6 octahedra, CsO6 octahedra, and BO3 triangles. Interestingly, CsCdBO3 crystallizes in the cubic space group P213, which is quite rare for borate-containing anisotropic polarized planar BO3 groups. Furthermore, the IR spectrum confirms the presence of BO3 groups. Second harmonic generation (SHG) measurements on powder samples reveal that the SHG response of CsCdBO3 is approximately 0.5 × KDP (KH2PO4). Thermal analysis and UV/Vis/NIR diffuse reflectance spectroscopy data, as well as electronic band structure calculations, are also reported. [ABSTRACT FROM AUTHOR]

Tables of alphanumeric data concerning crystals twinned by merohedry are presented, assembled into a spreadsheet. The twin table is structured on the 230 space groups and contains the following information: centrosymmetric/chiral indicator, polar axes, twin index, twin operators, some physical property relations, symmetry-related reflections, inversion techniques and a pointer to software use. The software table contains the preceding information translated into command lines for SHELXL [Sheldrick (2008). Acta Cryst. A 64, 112-122]. The macromolecular table contains a reduced form of the twin table applicable to enantiomerically pure compounds of known absolute configuration. [ABSTRACT FROM AUTHOR]

Polar magnetic materials exhibiting appreciable asymmetric exchange interactions can potentially host new topological states of matter such as vortex-like spin textures; however, realizations have been mostly limited to half-integer spins due to rare numbers of integer spin systems with broken spatial inversion lattice symmetries. Here, we studied the structure and magnetic properties of the S = 1 integer spin polar magnet β-Ni(IO3)2 (Ni2+, d8, 3F). We synthesized single crystals and bulk polycrystalline samples of β-Ni(IO3)2 by combining low-temperature chemistry techniques and thermal analysis and characterized its crystal structure and physical properties. Single crystal X-ray and powder X-ray diffraction measurements demonstrated that β-Ni(IO3)2 crystallizes in the noncentrosymmetric polar monoclinic structure with space group P21. The combination of the macroscopic electric polarization driven by the coalignment of the (IO3)− trigonal pyramids along the b axis and the S = 1 state of the Ni2+ cation was chosen to investigate integer spin and lattice dynamics in magnetism. The effective magnetic moment of Ni2+ was extracted from magnetization measurements to be 3.2(1) µB, confirming the S = 1 integer spin state of Ni2+ with some orbital contribution. β-Ni(IO3)2 undergoes a magnetic ordering at T = 3 K at a low magnetic field, μ0H = 0.1 T; the phase transition, nevertheless, is suppressed at a higher field, μ0H = 3 T. An anomaly resembling a phase transition is observed at T ≈ 2.7 K in the Cp/T vs. T plot, which is the approximate temperature of the magnetic phase transition of the material, indicating that the transition is magnetically driven. This work offers a useful route for exploring integer spin noncentrosymmetric materials, broadening the phase space of polar magnet candidates, which can harbor new topological spin physics. [ABSTRACT FROM AUTHOR]

Abstract: This review provides a survey of nonlinear optical (NLO) chromophores and materials incorporating them which have been demonstrated over the last several years. Conventional polymeric materials, dendrimers, and other material design approaches are reviewed. Macroscopic nonlinear optical properties are introduced mainly in terms of second-harmonic generation (SHG) and the electro-optic (EO) effect. The temporal and thermal stability of nonlinear optical properties are also discussed. The review begins with a brief introduction explaining overall principles relating to the origin of second-order nonlinear optical properties. The structure of NLO materials, methods for their characterization, and structure–property relationships are also introduced. Much current research is aimed at optimizing microscopic nonlinearity in well-defined heterocyclic NLO chromophores which are then embedded in materials such as polymers, dendrimers, etc. Strong electron density donor and acceptor groups are connected through an efficient π-electron conjugative bridge to yield a highly electronically asymmetric and hyperpolarizable NLO chromophore. This review highlights the design and synthesis of recent chromophores that simultaneously exhibit large molecular hyperpolarizability, and low optical absorption at an operating wavelength, in addition to good processability and thermal/photochemical stability. Although NLO chromophores have been designed to exploit both dipolar and octupolar symmetry, the former has exhibited the strongest potential for the development of practical NLO devices. Organic materials based on polymers and dendrimers containing dipolar chromophores are mainly demonstrated for nonlinear optics. Experimental results corresponding to such dipolar compounds are mainly considered in this review. In addition, new strategies to improve thermal stabilities are also discussed herein. [Copyright &y& Elsevier]

Abstract: A new noncentrosymmetric three-dimensional tellurite with second-order nonlinear optical property, BaMo2Te2O11(H2O), was synthesized by the hydrothermal reaction of Ba(OH)2, TeO2 and MoO3. It is characterized by single-crystal X-ray diffraction and spectral properties. The compound contains {Mo(1)Mo(2)O10} n infinite spiral chains, which are linked into infinite anionic layers along ab plane by Te(1)O5 and Te(2)O4 polyhedra. Ba2+ cations are intercalated between the layers. Energy band of the compound is calculated and analyzed, the band gap is 3.23eV, it indicates the solid-state compound of BaMo2Te2O11(H2O) is an insulator and the value is consistent well with the experimental value of 3.18eV. [Copyright &y& Elsevier]

Nonlinear optical (NLO) properties of three chiral smectic liquid crystals were investigated by Hyper-Rayleigh Scattering (HRS) and the Second-Harmonic Generation (SHG) methods. The HRS measurements of two compounds (MHPOBC and D16), with the biphenyl unit in their center, in solution demonstrate the quadratic NLO activity. The third compound (D17), having three isolated phenyl rings in the core, does not exhibit the NLO activity. The NLO properties in smectic phases of all investigated compounds have been also studied by wide-field second-harmonic and two-photon fluorescence microscopy confirming noncentrosymmetry for compounds with biphenyl π coupling (MHPOBC and D16). • Nonlinear optical properties of chiral smectic liquid crystals reported. • SHG and 2PF microscopy were used to obtain images of ferroelectric liquid crystals. • Comparison of NLO responses in ferro- and antiferroelectric SmC phases • Presence of p-conjugated biphenyl core important for quadratic NLO activity [ABSTRACT FROM AUTHOR]

• Thiosemicarbazidezincchloride (TSCZC) single crystals were grown via solution slow evaporation technique. • The optical band gap was around 4.54e V with 85 % of transmittence. • TSCZC crystal show 0.317 times SHG efficiency and can thermally stable upto 148 °C. • Non linear optical parameters β, n 2 and χ (3) were determined through Z scan analysis. • The grown, noncentrosymmetric NLO crystal can be applied for optic and photonic device applications. In this present work, we report the successful growth of zincchloride added thiosemicarbazide(TSCZC) crystals grown by slow solvent evaporation at room temperature. Good crystaline Pnma space group with orthorhombic structured non centrosymmetric crystal verified by powder-x ray diffraction was also characterised by Fourier Transformed Infrared, Differential Scanning Calorimetry and dielectric analysis to identify the presence of various functional groups with bonding types, thermal stability, and dielectric properties. Vast transparency in the whole visible region with 4.54 eV band gap for λ min = 273 nm suggests the utility of the crystal for non linear optical applications. Kurtz-Perry SHG test shows 0.317 times higher efficiency than reference KDP.Z scan analysis exhibits higher third order nonlinear optical susceptibility χ(3) = 3.266 × 10 - 6 esu with non linear refractive index(n 2) = 3.33 × 10 - 9 cm2/W.Self defocusing nature and Reverse Saturation Absorption(RSA) styles are the added advantages of the grown TSCZC metal organic crystal for its utilisability in Non Linear Optical and photonic device applications. [ABSTRACT FROM AUTHOR]

In this work we investigate the properties of elastic waves propagating in gyroid lattices. First, we rigorously characterize the lattice from the point of view of crystallography. Second, we use Bloch–Floquet analysis to compute the dispersion relations for elastic waves. The results for very long wavelengths are then compared to those given by classic elasticity for a cubic material. A discrepancy is found in terms of the polarization of waves and it is related to the noncentrosymmetry of the gyroid. The gyroid lattice results to be acoustically active, meaning that transverse waves exhibit a circular polarization when they propagate along an axis of rotational symmetry. This phenomenon is present even for very long wavelengths and is not captured by classic elasticity. [ABSTRACT FROM AUTHOR]

Non-centrosymmetric structure is the most important prerequisite for a nonlinear-optical (NLO) material. Herein, a non-centrosymmetric phosphate LiRb 2 Y 2 (PO 4) 3 (1), which is transparent down to ultraviolet region, was synthesized by the high-temperature solid-state reactions and solution method. Its crystal structure features a three-dimensional framework composed of corner-sharing YO 6 octahedra and PO 4 tetrahedra. Although it is isostructural to the known langbeinite-type sulfate K 2 Zn 2 (SO 4) 3 , 1 exhibits a sharply enhanced NLO effect (about 3 times that of K 2 Zn 2 (SO 4) 3). On the basis of structural analysis and theory calculations, the improved performance of compound 1 is mainly ascribed to the aliovalent replacement of ZnO 6 by YO 6 octahedra. Our studies indicated that it may be an effective method to develop non-centrosymmetric compounds by aliovalent substitution. By aliovalent-substituted synthesis method based on K 2 Zn 2 (SO 4) 3 , a new phosphate LiRb 2 Y 2 (PO 4) 3 was synthesized and exhibits a sharply enhanced second-harmonic generation (SHG) effect. Image 1 [ABSTRACT FROM AUTHOR]

Electrical-to-optical signal conversion is widely employed in information technology and is implemented using on-chip optical modulators. State-of-the-art modulator technologies are incompatible with silicon manufacturing techniques: inorganic nonlinear crystals such as LiNbO 3 are integrated with silicon photonic chips only using complex approaches, and hybrid silicon-LiNbO 3 optical modulators show either low bandwidth or high operating voltage. Organic perovskites are solution-processed materials readily integrated with silicon photonics; and organic molecules embedded within the perovskite scaffold allow in principle for high polarizability. However, it is found that the large molecules required for high polarizability also require an increase of the size of the perovskite cavity: specifically, using the highly polarizable DR 2+ (R = H, F, Cl) in the A site necessitates the exploration of new X-site options. Only by introducing BF 4 - as the X-site molecule is it possible to synthesize (DCl)(NH 4 )(BF 4 ) 3 , a material exhibiting a linear EO coefficient of 20 pm V -1 , which is 10 times higher than that of metal halide perovskites and is a 1.5 fold enhancement compared to reported organic perovskites. The EO response of the organic perovskite approaches that of LiNbO 3 (r eff  ≈ 30 pm V -1 ) and highlights the promise of rationally designed organic perovskites for use in efficient EO modulators., (© 2020 Wiley-VCH GmbH.)