Non-centrosymmetric Space Group Research Articles

Space Group Choice for an Octahedral Zn Complex with Nalidixic Acid and (R,R)-Diaminocyclohexane as Ligands: Get the Stereochemistry Right

With this report, the space group of [Zn(Nal)(DACH)2]Cl is corrected (Nal: nalidixic acid mono-anion; DACH: diaminocyclohexane) from its wrong description in the literature. In the correct, non-centrosymmetric space group P1, the crystal structure is well ordered and the stereochemistry is correct. Crystallographic tools to recognize the correct symmetry are described. This work encourages experienced and inexperienced scientists to remain critical about the output of automatic, black-box crystallographic software.

Nonlinear Optical Effects of Hybrid Antimony(III) Halides Induced by Stereoactive 5s2 Lone Pairs and Trimethylammonium Cations.

Organic-inorganic hybrid metal halides have unique optical and electronic properties, which are advantageous in the study of nonlinear optical materials. To investigate the effect of stereoactive lone pair electrons and the induction of organic cations on the structure of hybrid antimony(III) halides on nonlinear optics, we synthesize two noncentrosymmetric hybrid antimony(III)-based halide single crystals (TMA)3Sb2X9 (TMA = NH(CH3)3+, X = Cl, Br) by a room-temperature slow evaporation method, and their single-crystal structures, phase transition, X-ray photoelectron spectroscopy, and energy-band structure calculations are studied. More importantly, second-harmonic generation results of (TMA)3Sb2X9 (X = Cl, Br) are about 0.7 and 0.8 × KH2PO4(KDP), respectively. Interestingly, (TMA)3Sb2Cl9 single crystals undergo a reversible structural transition from Pc (No. 7) at room temperature to P21/c (No. 14) at 400 K, while the (TMA)3Sb2Br9 single crystals belong to the noncentrosymmetric space group R3c (No. 161), which clarifies the previous results. This work not only deepens the understanding of the role in lone pair electrons and organic cations in the structural induction in antimony-based halide perovskite materials but also provides guidance for subsequent nonlinear optical explorations.

Nonlinear Optical Activity of a Chiral Organic-Inorganic ([(NH3CH2CH2)3NH])2[MnBr5]Br5 Photoluminescent and Piezoelectric Crystal.

The family of Mn-based organic-inorganic hybrids has greatly expanded due to their advantages in applications. They also show superior bright and size-tunable photoluminescence and can be considered a perfect alternative to toxic lead-based compounds. In this work, we present the detailed structural, optical, and electrical characterization of ([(NH3CH2CH2)3NH])2[MnBr5]Br5. The title compound exhibits a unique type of inorganic arrangement created by the trigonal bipyramids. It crystallizes in noncentrosymmetric space group R32, indicating its optical activity, piezoelectricity, and second-order optical nonlinearity proven by the second harmonic of light measurements. The studied crystals exhibit intense photoluminescence originating from the Mn(II) ion 4T1(G) → 6A1 transition. The measured lifetime of the photoluminescence emission is ≤1.5 ms, while the measured quantum yield for both powder and crystal samples reaches ∼70%.

Circularly Polarized Luminescence Induced by Hydrogen-Bonding Networks in a One-Dimensional Hybrid Manganese(II) Chloride.

Chiral hybrid metal halides hold great potential as circularly polarized luminescence light sources. Herein, we have obtained two enantiomeric pairs of one-dimensional hybrid chiral manganese(II) chloride single crystals, R/S-(3-methyl piperidine)MnCl3 (R/S-1) and R/S-(3-hydroxy piperidine)MnCl3 (R/S-2), crystallizing in the non-centrosymmetric space group P212121. In comparison to R/S-1, R/S-2 single crystals not only show red emission with near-unity photoluminescence quantum yield (PLQY) and high resistance to thermal quenching but also exhibit circularly polarized luminescence with an asymmetry factor (glum) of 2.5×10-3, which can be attributed to the enhanced crystal rigidity resulting from the hydrogen bonding networks between R/S-(3-hydroxy piperidine) cations and [MnCl6]4- chains. The circularly polarized luminescence activities originate from the asymmetric [MnCl6]4- luminophores induced by N-H⋅⋅⋅Cl hydrogen bonding with R/S-(3-hydroxy piperidine). Moreover, these samples demonstrate great application potential in circularly polarized light-emitting diodes and X-ray scintillators. This work shows a highly efficient photoluminescent Mn-based halide and offers a strategy for designing multifunctional chiral metal halides.

Chiral Heterometallic Cu8Ln4 Complexes with Enantiopure Schiff Base Ligands: Synthesis, Structural, Spectroscopic and Magnetic Studies.

The enantiomerically pure Schiff base ligands H2L-S and H2L-R yield chiral heterometallic dodecanuclear complexes of the form [Cu8Ln4(OH)8(OMe)4(O2CBut)8(L-S or L-R)4(H2O)4] where LnIII=Gd (1S), Tb (2S), Dy (3S, 3R), Ho (4S, 4R), Er (5S) or Y (6S, 6R) and H2L=(S or R)-2-{[(1-hydroxypropan-2-yl)imino]methyl}-6-methoxyphenol. The complexes are isomorphous and crystallize in the non-centrosymmetric polar space group C2 in enantiomeric conformation. The chirality of the Schiff base ligands originates from the respective S- or R- enantiomer of 2-aminopropan-1-ol, is imparted to the complexes and to the crystals that belong to non-centrosymmetric space group. The chirality and enantiomeric conformation of all complexes are retained in dmso solutions as confirmed by Circular Dichroism spectra which consist of mirror images, expected for enantiomeric pairs. All complexes consist of four distorted cubane-like subunits [Cu2Ln2(μ3-OH)2(μ3-OMe)(μ3-OR)], which share the LnIII ions and result in a cyclic distorted tetragonal arrangement; each edge of the {LnIII 4} quadrilateral is occupied by two μ-OH- ions that further bridge to a CuII ion. Magnetic susceptibility measurements revealed ferromagnetic interactions for 3S with LnIII=Dy and antiferromagnetic interactions for all other complexes. AC susceptibility data of 3S under 1 kOe external dc field indicate slow magnetic relaxation phenomena below 2 K.

Ferroelectric Organic-Inorganic Hybrid Ammonium Halogenobismuthate(III) for Piezoelectric Energy Harvesting.

Halogenobismuthate(III) compounds are of recent interest because of their low toxicity and distinct electrical properties. The utility of these materials as ferroelectrics for piezoelectric energy harvesters is still in its early stages. Herein, we report a hybrid ammonium halogenobismuthate(III) [BPBrDMA]2·[BiBr5], crystallizing in a ferroelectrically active polar noncentrosymmetric Pna21 space group. Its noncentrosymmetric structure was confirmed by the detection of the second harmonic generation response. The ferroelectric P-E hysteresis loop measurements on the thin film sample of [BPBrDMA]2·[BiBr5] gave a saturation polarization (Ps) of 5.72 μC cm-2. The piezoresponse force microscopy analysis confirmed its ferroelectric and piezoelectric nature, showing characteristic domain structures and signature hysteresis and butterfly loops. The piezoelectric energy harvesting attributes of [BPBrDMA]2·[BiBr5] were further probed on its polylactic acid (PLA) composites. The 15 wt % [BPBrDMA]2·[BiBr5]-PLA polymer composite resulted in a high output voltage of 26.2 V and power density of 15.47 μW cm-2. The energy harvested from this device was further utilized for charging a 10 μF capacitor within 3 min.

LaMg6Ga6S16: a chemical stable divalent lanthanide chalcogenide

Divalent lanthanide inorganic compounds can exhibit unique electronic configurations and physicochemical properties, yet their synthesis remains a great challenge because of the weak chemical stability. To the best of our knowledge, although several lanthanide monoxides epitaxial thin films have been reported, there is no chemically stable crystalline divalent lanthanide chalcogenide synthesized up to now. Herein, by using octahedra coupling tetrahedra single/double chains to construct an octahedral crystal field, we synthesized the stable crystalline La(II)-chalcogenide, LaMg6Ga6S16. The nature of the divalent La2+ cations can be identified by X-ray photoelectron spectroscopy, X-ray absorption near-edge structure and electron paramagnetic resonance, while the stability is confirmed by the differential thermal scanning, in-situ variable-temperature powder X-ray diffraction and a series of solid-state reactions. Owing to the particular electronic characteristics of La2+(5d1), LaMg6Ga6S16 displays an ultrabroad-band green emission at 500 nm, which is the inaugural instance of La(II)-based compounds demonstrating luminescent properties. Furthermore, as LaMg6Ga6S16 crystallizes in the non-centrosymmetric space group, P−6, it is the second-harmonic generation (SHG) active, possessing a comparable SHG response with classical AgGaS2. In consideration of its wider band gap (Eg = 3.0 eV) and higher laser-induced damage threshold (5×AgGaS2), LaMg6Ga6S16 is also a promising nonlinear optical material.

Synthesis under high pressure: crystal structure and properties of cubic Dy36O11F50[AsO3]12 ∙ H2O.

The multi-anionic compound with the composition Dy36O11F50[AsO3]12 ∙ H2O, which can be described in the non-centrosymmetric cubic space group F c, already shows an unusually large unit cell with an axis of a = 2587.59(14) pm. Its crystal structure exhibits isolated ψ1-tetrahedral [AsO3]3- anions, but both the coordination numbers and the linking schemes of the Dy3+-centered polyhedra differ significantly from the mostly layered structures described so far in literature. (Dy1)3+ is sevenfold coordinated by oxygen atoms and F- anions, forming a capped trigonal prism [(Dy1)O4.333F2.667]8.333-, and the remaining two cations (Dy2)3+ and (Dy3)3+ both reside in an eightfold coordination of anions. In both cases they form slightly distorted square antiprisms, which have the compositions of [(Dy2)O3.667F4.333]8.667- and [(Dy3)O4.667F3.333]9.667-, respectively. Some of the oxygen atoms are not part of ψ1-[AsO3]3- tetrahedra, but occur as O2- anions and one of these even shares a common crystallographic position with fluoride (F-). It is also worth mentioning that the single crystals were obtained as comparatively large cubes with an edge length of several 100µm providing very good data with regard to single-crystal X-ray diffraction. To verify the simultaneous presence of oxygen and fluorine, electron-beam microprobe analysis was carried out, and a single-crystal Raman spectrum ruled out the presence of hydroxide anions or protonated [AsO3]3- groups, but proved the interstitial crystal-water molecules, which could not be determined precisely by the crystal-structure refinement.

Exploring the physicochemical properties of a new mixed halide 1D hybrid material Zn(C2H8N2)Br1.41Cl0.59 with a non-centrosymmetric structure: Promising material for nonlinear applications

Colorless crystals of a new mixed halide hybrid material, Zn(C2H8N2)Br1.41Cl0.59, were synthesized by the slow evaporation method at room temperature. The crystal structure, thermal behavior, and optical analysis were analyzed to characterize this complex. The crystal structure study revealed that this compound adopts the orthorhombic system and crystallizes in the non-centrosymmetric space group Ima2. Its one-dimensional structure is built from infinite wavy chains of [Zn(C2H8N2)Br1.41Cl0.59]n propagating along the crystallographic a-axis, which are interconnected through NH···Br/Cl hydrogen bonds. Thermogravimetric analysis indicated that this complex remains stable up 251 °C, decomposing in a single step to yield zinc oxide (ZnO) as final product. Differential scanning calorimetry (DSC) revealed an endothermic peak at 195 °C, indicating that the title compound undergoes a phase transition at this temperature. Additionally, the material's suitability for optical application was assessed through UV–Visible absorption and non-linear optical (NLO) techniques. The determined band gap energy of 4.5 eV suggests that this new complex can be classified as a semiconductor material closely resembling an insulator. Furthermore, the second harmonic generation (SHG) efficiency of the grown crystal was analyzed using the Kurtz-Perry powder technique. The IR and Raman spectra confirm the results obtained from X-ray single-crystal structural analyses.

Synthesis of novel supramolecular selenomolybdate as anticancer agents: An experimental and DFT computational analysis

A novel organic–inorganic material based on three-dimensional (3D) Strandberg-type polyoxoselenomolybdate, (C6H14N2)2[Se2Mo5O21]·2·6H2O (I, where C6H14N2 = DABCO cation) was successfully synthesized by solution process and characterized by scanning electron microscopy (SEM), infrared (FT-IR) and ultraviolet (UV–vis) spectroscopies, thermogravimetric analysis (TGA), cyclic voltammetry (CV) measurement. The electronic and electrochemical behavior of the compound was further evaluated as a function of pH and time via UV–vis spectroscopy and CV. Single crystal X-Ray diffraction (XRD) technique was used for complete structure elucidation. The title compound crystallizes in the non-centrosymmetric orthorhombic space group P212121, thus resulting in non-linear optical properties. The supramolecular framework exhibits a periodic arrangement of Strandberg clusters anions [Se2Mo5O21]4– connected to each other with water molecules and dabconium cations, through a network of hydrogen bonds and van der Waals interactions. The occurrence of intermolecular interactions, ensuring the cohesion between different entities, was assessed by density functional theory (DFT) calculations and Hirshfeld surface analysis. DFT calculations with different functionals have been used to better understand several properties like as RDG, QTAIMs, ELF, MEP and NLO.A good agreement was indeed found between the experimental and computational results. Furthermore, the (C6H14N2)2[Se2Mo5O21]·2·6H2O compound was tested for its biological activity. This selenomolybdate displayed a significant inhibitory effect on the growth of human ovarian cancer cells A2780, with an IC50 value of 4.05 ± 0.55 μM, being thus the first Strandberg-type polyoxometalate to show a significant anticancer activity.

Optical, electrical and thermal investigations on brucinium di-hydrogen citrate tri-hydrate single crystal: An optimistic tool for microelectronics, OPO and OLED applications

Highly capable nonlinear optical brucinium di-hydrogen citrate tri-hydrate (BDHCTH) single crystal under organic material category has been grown-up successfully by slow evaporation method. Optical, electrical, and thermal investigations were made on title crystal to discover the suitability of fabrication of an optical as well as electrical device for the first time. Crystal structure analysis confirms that, the BDHCTH crystal belongs to triclinic crystal system with non-centro symmetric space group P1. The SLDT value of BDHCTH crystal was found to be 4.22 GW/cm2. Second harmonic generation efficiency of the BDHCTH compound is 1.08 times superior to the reference sample KDP. An attribution of single and sharp peak with lesser full width half maximum value confirms the presence of very fewer defects in the grown crystal. An electric response of the title compound shows the normal dielectric behavior. The piezoelectric charge co-efficient (d33) was found to be 4.5 p C/N. Photo luminescence study confirms that the synthesized sample possess violet, blue and red emission behaviors. Presences of various functional groups in the title sample were identified by FT-IR study. Thermal stability of the compound BDHCTH was found to be 135 °C. Kinetic parameters such as activation energy, Arrhenius factor, standard entropy of activation, standard enthalpy of activation, standard Gibb's energy of activation (ΔG*) and induction time of the grown sample were found to be 161.6396 k J mol−1, 7.4854 s−1, -230.8278 J K mol−1, 154.854 k J mol−1, 249.0314 k J mol−1 and 52 days respectively. At the end of an optical, electrical and thermal analysis, we concluded that the grown crystal is an optimistic tool for microelectronics, OPO and OLED applications due to existence of good SHG value, lesser defect and red emission behavior.

Prospective light-harvesting material of L-phenylalaninium selenate monohydrate: Synthesis, thermal behavior, vibrational and optical properties

The present work focuses on the study of a new organo-selenate hybrid material, namely [C9H12NO2]2SeO4.H2O, abbreviated as (LPA)2.SeO4.H2O, which was successfully obtained at room temperature by slow evaporation. The structure was studied by the X-ray single-crystal diffraction process. This compound crystallizes in the monoclinic system, with a non-centrosymmetric P21 space group and the following lattice parameters: a = 12.817(3) Å; b = 6.272(15) Å; c = 13.629(3) Å, β=103.847(7)°, Z = 2 and V = 1063.7(4) Å3. The atomic arrangement in the structure is described as an alternation of organic and inorganic entities along the a-axis. The IR and Raman spectra were recorded in the 500–4000 cm-1 and 10–4000 cm-1 frequency region, respectively, confirming the existence of vibrational modes that correlate with organic and inorganic groups. The crystal arrangement is determined by hydrogen bonds of the type NH…O, OH…O and OW-H…O. The intermolecular interactions in the crystal structure were quantified and analyzed using Hirshfeld surface analysis. TGA-DTG and DSC analyses have shown that compound dehydration at around 90°C produces an anhydrous compound that is thermically stable until 122°C. Experimental UV–Visible absorption of the compound demonstrated its semiconducting properties, revealing a direct optical band gap at 5.53 eV. Finally, photoluminescence measurements indicate that the synthesized material exhibits solid-state luminescence properties. Optimized geometry and HOMO-LUMO were calculated using the B3LYP/6–311+ G(dd,p) basis set. The theoretical calculations performed by density functional theory are in agreement with the experimental results obtained.

Guanidinium Vanadate [C(NH2)3]3VO4·2H2O Revealing Enhanced Second-Harmonic Generation and Wide Band Gaps.

A new guanidinium-templated vanadate, [C(NH2)3]3VO4·2H2O, has been synthesized in a phase-pure form. It crystallizes in a noncentrosymmetric polar space group, Cc, and the crystal structure is built upon a framework of guanidinium, vanadate tetrahedra, and water molecules linked by hydrogen bonds. Notably, optical measurements reveal that the material exhibits an approximately 9.6-fold enhancement in second-harmonic generation efficiency compared to its phosphate analogue. The enhancement can be attributed to the increased geometrical distortion of the VO4 tetrahedra. Furthermore, we found that the coordination number of the central vanadium atom significantly affects the optical band gaps. Among various coordination numbers, the 4-coordinate VO4 tetrahedra are found to be more favorable for widening the optical band gap of materials compared to the 5- and 6-coordinate vanadium polyhedra, as demonstrated by this work.

Borosilicate-Based Framework: Synthesis, Single-Crystal Structure Study, and Physical Properties.

Herein, we report the synthesis, crystal structure, and optical properties of a metal-free three-dimensional (3D) inorganic covalent framework ((H2en)[Si(B4O9)], named CityU-11, where H2en is the abbreviation for ethanediamine). With the assistance of a tiny amount of F- ions and the selection of SiO2 as Si sources, single crystals of CityU-11 can be successfully prepared under solvothermal conditions. The precise structure information on CityU-11 has been disclosed through both single-crystal X-ray diffraction (SCXRD) and low-dose high-resolution transmission electron microscopy (LD-HRTEM). The SCXRD results showed that CityU-11 crystallized in the noncentrosymmetric space group of Pnn2, while LD-HRTEM suggested that CityU-11 possessed almost the same interplanar distances of 0.6 nm for both (200) and (020) crystal planes, which finely matched with the double peaks of 2θ = 15° in the pattern of its powder X-ray diffraction (PXRD). CityU-11 also displayed an interesting optical property with a moderate birefringence of 0.0258@550 nm.

Symmetry-enforced fourfold degenerate phonons in noncentrosymmetric space groups

Multifold degenerate phonons have received much attention due to their nontrivial monopole topological charge and fascinating boundary states. Although Yu et al recently provides a comprehensive list of all potential nodal points for systems with specific space groups (SGs) (2022 Sci. Bull. 67 375). However, our understanding of the fundamental mechanisms that give rise to the formation of fourfold-degenerate (FD) phonons is still limited. In this paper, we have directed our research towards investigating the generation mechanism of these FD phonons in noncentrosymmetric SGs. Using symmetry arguments and k⋅p model analysis, we have classified them into two categories: the first origins from the commutation/anticommutation relation of the little cogroup operations, and the second associates to the combination of threefold rotation, mirror and time-reversal symmetries. Moreover, the band dispersions of the FD phonons in the first group are required to be linear, whereas the band dispersions of the FD phonons in the second category may be quadratic. On the basis of first-principles calculations, we propose that K 2 Mg2O3 and Na 4 SnSe4 are representative candidates for the two categories, respectively. Furthermore, for each SG with fourfold degenerate phonons, we propose corresponding materials that must host the FD points. Our work not only deepens our understanding of the mechanisms underlying the formation of these FD phonons, but it also proposes practical materials for observing FD phonons in crystalline systems without inversion symmetry.

Topological Nodal-Point Superconductivity in Two-Dimensional Ferroelectric Hybrid Perovskites.

Two-dimensional (2D) hybrid organic-inorganic perovskites (HOIPs) with enhanced stability, high tunability, and strong spin-orbit coupling have shown great potential in vast applications. Here, we extend the already rich functionality of 2D HOIPs to a new territory, realizing topological superconductivity and Majorana modes for fault-tolerant quantum computation. Especially, we predict that room-temperature ferroelectric BA2PbCl4 (BA for benzylammonium) exhibits topological nodal-point superconductivity (NSC) and gapless Majorana modes on selected edges and ferroelectric domain walls when proximity-coupled to an s-wave superconductor and an in-plane Zeeman field, attractive for experimental verification and application. Since NSC is protected by spatial symmetry of 2D HOIPs, we envision more exotic topological superconducting states to be found in this class of materials due to their diverse noncentrosymmetric space groups, which may open a new avenue in the fields of HOIPs and topological superconductivity.

Die Serie caesiumhaltiger Thioarsenate(V) der Lanthanoide vom Formeltyp Cs3 Ln[AsS4]2 mit Ln = La–Nd und Sm

Abstract Cesium-containing thioarsenates(V) of lanthanoids with the composition Cs3 Ln[AsS4]2 can be prepared for Ln = La–Nd and Sm by the oxidation of the lanthanoid metals in the presence of orpiment (As2S3), cesium sesquisulfide (Cs2S3) and elemental sulfur (S). The reaction mixtures were handled under argon atmosphere and heated in fused silica ampoules to a moderate reaction temperature of 500 °C. Single crystals of this Cs3 Ln[AsS4]2 series appear as yellowish, transparent rods that are not stable to moist air and water. Their monoclinic crystal structure was determined from single-crystal X-ray diffraction data. The cesium-containing thioarsenates(V) Cs3 Ln[AsS4]2 with Ln = La–Nd and Sm crystallize isotypically with Rb3Sm[PS4]2 in the non-centrosymmetric monoclinic space group P21 with Z = 2. The lattice parameters range between a = 997–1015 pm, b = 699–703 pm, c = 1192–1195 pm and β = 90.2–90.4°. There are two crystallographically different As5+ cations and one unique Ln 3+ cation present, all coordinated by sulfur anions. Tetrahedral [AsS4]3− anions form two functionally different units working either as bridging units between three Ln 3+ cations or as terminal ligands for Ln 3+. [LnS8]13− polyhedra form ∞ 1 { [ Ln S 2 / 2 v S 6 / 1 t ] 11 − } ${}_{\infty }^{1}\left\{{[\mathit{Ln}{\mathrm{S}}_{2/2}^{\mathrm{v}}{\mathrm{S}}_{6/1}^{\mathrm{t}}]}^{11-}\right\}$ chains propagating along [010], which are separated by Cs+ cations with coordination numbers as high as C.N. = 9, 10 and 11. Surprisingly, the eighth interatomic distance d(Ln–S3) does not follow the lanthanoid contraction, but increases with decreasing ionic radius, changing the coordination polyhedron of Ln 3+ from a bicapped to a monocapped trigonal prism upon the transition from Nd to Sm, and causing a structural break in the crystal structure of this series. The results of Raman spectroscopic measurements on single crystals of Cs3La[AsS4]2 have confirmed the presence of [AsS4]3− tetrahedra as structural building blocks.

Crystal growth, structural, optical, mechanical characterization and quantum chemical analysis by DFT of an organic nonlinear optical single crystal 4-Hydroxy pyridinium succinate for photonic and optoelectronic devices

A new organic nonlinear optical single crystal 4-Hydroxypyridinium Succinate was synthesized and grown successfully by slow evaporation method using methanol as solvent at ambient temperature. Single crystal X –ray diffraction studies on the grown crystal reveals that 4HPS crystallizes into orthorhombic structure with the non-centrosymmetric space group (Pna21). In structural point of view, the 4-Hydroxypyridinium cation is bonded to the hydrogen succinate anion by direct electron conjugation through nitrogen atom. In addition, the UV visible transmittance spectrum implies that the crystal has high transparency domain in the entire UV visible region with a lower cut-off wavelength of 286 nm. The various functional groups present in the crystal and their frequency assignments are derived from FTIR spectral analysis. The Photoluminescence spectrum brings forth that the grown crystal has violet emission property. The microhardness measurements testify that the crystal belongs to soft material category with reasonable hardness parameters. The compound was found to be thermally stable up to 188 °C without any weight loss from the TGA and DTG traces. The detailed quantum chemical calculation done by density functional theory (DFT) indicates the Homo –Lumo energy gap of the molecule is 3. 956 eV and 4. 289 eV for α and β wave functions respectively. The Laser induced damage threshold of the crystal investigated using Nd: YAG laser of 1064 nm radiation was found to be 21. 93 Gw/cm2. The second harmonic generation efficiency of the 4HPS crystal was confirmed by the emission of green light under Kurtz and Perry powder test.

Synthesis, structure, growth, characterization and quantum chemical studies on 2-amino-5-bromopyridinium trichloroacetate: A novel phasematchable organic NLO single crystal

Organic crystals have become excellent candidates towards nonlinear optical (NLO) applications as they possess superior second and third order optical nonlinearities and high electro-optic coefficients when compared with their inorganic counterparts. In this direction, 2-Amino-5-bromopyridinium trichloroacetate (2A5BPT), a new organic second-order nonlinear optical compound is synthesized and optical grade single crystals are formed utilizing a slow evaporation solution growth approach at room temperature while using methanol as the solvent. Single crystal X-ray diffraction study shows that the title compound is assigned to monoclinic crystal system having non-centrosymmetric space group Cc. The crystal is transparent ( ̴ 85%) throughout the whole visible spectrum, according to the Ultraviolet-Visble (UV–Vis) spectra, with a cutoff wavelength of 367 nm and an optical energy band gap Eg of 3.32 eV. The crystal possesses good thermal stability. The compound has a 1.6 times greater powder second harmonic generation (SHG) efficiency than potassium dihydrogen phosphate (KDP). The phase matchability of the 2A5BPT is studied through particle size dependence of SHG. The intermolecular connection demonstrated by numerous inter contacts has been shown by a molecular Hirshfeld surface analysis of the crystal structure, and the related 2-dimensional finger print analysis further evaluates the individual contribution from each atom. In order to examine the first order hyperpolarizability, molecular electrostatic potential, and Highest occupied molecular orbital-Lowest unoccupied molecular orbital (HOMO-LUMO) energies, the quantum chemical calculations for the title molecule (2A5BPT) were carried out by density functional theory (DFT) utilizing the B3LYP/6–311++G(d,p) basis set. According to these results, the 2A5BPT crystal could be suitable for optoelectronic applications.

Crystal structure and properties of perovskite-type rubidium niobate, a high-pressure phase of RbNbO3.

We synthesized a perovskite-type RbNbO3 at 1173 K and 4 GPa from non-perovskite RbNbO3 and investigated its crystal structure and properties towards ferroelectric material design. Single-crystal X-ray diffraction analysis revealed an orthorhombic cell in the perovskite-type structure (space group Amm2, no. 38) with a = 3.9937(2) Å, b = 5.8217(3) Å, and c = 5.8647(2) Å. This non-centrosymmetric space group is the same as the ferroelectric BaTiO3 and KNbO3 but with enhanced distortion. Structural transition from orthorhombic to two successive tetragonal phases (Tetra1 at 493 K, Tetra2 at 573 K) was observed, maintaining the perovskite framework before reverting to the triclinic ambient phase at 693 K, with no structural changes between 4 and 300 K. The first transition is similar to that of KNbO3, whereas the second to Tetra2, marked by c-axis elongation and a significant cp/ap ratio jump (from 1.07 to 1.43), is unique. This distortion suggests a transition similar to that of PbVO3, where an octahedron's oxygen separates along the c-axis, forming a pyramid. Ab initio calculations simulating negative pressure like thermal expansion predicted this phase transition (cp/ap = 1.47 at -1.2 GPa), aligning with experimental findings. Thermal analysis revealed two endothermic peaks, with the second transition entailing a greater enthalpy change and volume alteration. Strong second harmonic generation signals were observed across Ortho, Tetra1, and Tetra2 phases, similar to BaTiO3 and KNbO3. Permittivity increased during the first transition, although the second transition's effects were limited by thermal expansion-induced bulk sample collapse. Perovskite-type RbNbO3 emerges as a promising ferroelectric material.