Values Of Unit Cell Parameters Research Articles

Syntheses and characterization of noncentrosymmetric layered phosphates, Sr3Nb2P2O13 and Sr3Ta2P2O13

Two new isostructural quaternary phosphates, Sr3Nb2P2O13 and Sr3Ta2P2O13, were synthesized by solid-state reactions and characterized by X-ray diffraction, thermal and spectroscopic techniques. Sr3Nb2P2O13 compound, as determined by single crystal X-ray diffraction method, crystallizes in noncentrosymmetric P212121 space group with orthorhombic unit cell parameter values of a = 5.2713 (1) Å, b = 10.6570 (2) and c = 19.7155 (4) Å and has a unique layered structure consisting of Sr2+ and discrete PO43− ions between anionic [Nb2PO9]3- framework layers. The noncentrosymmetric structure is attributed to acentric coordination polyhedra, namely, distorted NbO6 octahedron and PO43− tetrahedron. The isostructural nature of Sr3Ta2P2O13 compound was deduced from powder X-ray diffraction data. Sr3Nb2P2O13 and Sr3Ta2P2O13 compounds, respectively, melt and decompose at ∼1200 °C and have band gap values of 3.86 and 3.64 eV.

Syntheses and characterization of quaternary selenites and tellurite of antimony, NaSbSe2O7, AgSbSe2O7 and Na2Sb4Te2O14

NaSbSe2O7, AgSbSe2O7 and Na2Sb4Te2O14 compounds have been synthesized by solid state reactions and characterized by single crystal X-ray diffraction, thermal analysis, reflectance spectroscopy, and second harmonic generation (SHG) response studies. The isostructural NaSbSe2O7 and AgSbSe2O7 selenites crystallize in centrosymmetric Cmcm space group with respective orthorhombic unit cell parameter values of a = 10.0704(4) and 10.0449(5) Å, b = 8.3074(4) and 8.3825(5) Å and c = 7.1449(3) and 7.1438(5) Å. Their one-dimensional structure consists of Na+ or Ag+ cations and anionic [SbSe2O7]- chains made up of SbO6 octahedra and SeO3 trigonal pyramids. Na2Sb4Te2O14 is a mixed-valent compound, which crystallizes in noncentrosymmetric P3121 space group with hexagonal unit cell parameter values of a = 7.32670(10) Å and c = 18.5150(5) Å. It has a three-dimensional hexagonal-tungsten-oxide (HTO) related anionic [Sb4Te2O14]2- structural framework and shows powder SHG response equivalent to 0.4 × KDP.

Syntheses, Crystal Structure, and Second Harmonic Generation Response of Noncentrosymmetric Layered Selenites and Tellurites of Antimony(V), ASb3X2O12 (A = K, Rb, Cs, Tl; X = Se, Te).

Eight quaternary selenites and tellurites of antimony(V), ASb3X2O12 (A = K, Rb, Cs, Tl; X = Se, Te), have been synthesized by solid state reactions and structurally characterized by single crystal X-ray diffraction. They are isostructural compounds, which crystallize in the polar noncentrosymmetric P63mc space group with hexagonal unit cell parameter values in the ranges of a = 7.1538(1)-7.2429(1) Å and c = 11.8978(4)-12.0478(3) Å. Their noncentrosymmetric layered structure consists of hexagonal-tungsten-oxide-related (Sb3X2O12)- layers interleaved with A+ ions. They have optical band gap values of 2.90-4.46 eV and showed powder second harmonic generation response equivalent to 1.0-37.2 × KDP.

Slow Phase Transition-Induced Scan Rate Dependence of Spin Crossover in a Two-Dimensional Supramolecular Fe(III) Complex

Slow Phase Transition-Induced Scan Rate Dependence of Spin Crossover in a Two-Dimensional Supramolecular Fe(III) Complex

Synthesis, structural analysis, Hirshfeld surface analysis, DFT calculations, in vitro and docking study on antioxidant activity of 6-chloro-3-[(4-methylphenoxy) methyl] [1,2,4] triazolo[4,3-b]pyridazine

Pyridazine nuclei are essential elements of many natural and synthetic compounds with important biological activities. NMR and IR, as well as studies of mass spectrum, were emplyed to synthesize and characterize the title compound 6-chloro-3-[(4-methylphenoxy) methyl] [1,2,4] triazolo[4,3-b] pyridazine (CMTP). The structure of this compound was confirmed by using single crystal X-ray diffraction technique and it got crystallized in the monoclinic crystal system with the space group P2 1/c. The values of unit cell parameters are: a = 12.0965(7) Å, b = 13.6075(7) Å, c = 7.7686(4) Å, β = 93.942(3)° and Z = 4. Intermolecular hydrogen bonds of two types i.e., C-H…O and C-H…N, were noticed. Hirshfeld surface analysis was employed to account for these interaction bonds. Energy frameworks were carried out to know the dominant interaction energy involved in the molecular packing. DFT calculations were constructed to find the agreement between the theoretical and experimental values. HOMO-LUMO energy levels have been determined; global hardness, global softness, and other quantum chemical parameters have been calculated to reveal the chemical reactivity of the compound. In order to investigate the antioxidant activity of the compound, molecular docking studies were performed.

Crystal growth, structural, nonlinear optical and theoretical investigations of Benzilic acid crystals

Organic single crystals of Benzilic Acid (BA) were grown by slow solvent evaporating method by using acetone as solvent. The unit cell parameter values and the crystal system are recognized by using single crystal XRD technique. The optical assessment of BA molecules is observed by with UV-Vis spectral analysis as the ultraviolet range between 200 and 400 nm and the visible region between 400 and 800 nm. The nonlinear optical (NLO) properties such as second harmonic efficiency nature of BA crystal were analyzed using Nd:YAG laser. The laser-induced damage threshold assessment of BA crystal is measured as 2.76 GW/cm2. From the Density Functional Theory (DFT), the molecular structural feature and vibrational frequencies were defined by using the Gaussian system along with comparisons of experimental frequencies. Using the DFT method, the derived vibrational frequency values showed an admirable accord with experimental frequencies. The charge interactions within the BA molecules are confirmed by HOMO and LUMO energy value. The first-order molecular hyperpolarizabilities, dipole moment, polarizability and Mulliken charge analysis of the BA molecule are also evaluated.

Growth and characterization of pure and cadmium dichloride doped aminoethanoic acid (AEA) single crystals

Organic and semiorganic centrosymmetry single crystals of pure and cadmium dichloride doped aminoethanoic acid was successfully grown by slow evaporation solution growth technique. The solubility of the grown crystals was studied for different temperatures upto 50 °C. The single crystal X-ray diffraction analysis shows that the grown crystal belongs to monoclinic system and their unit cell parameter values were determined. The presence of various functional groups was identified by Fourier transform infrared spectroscopy. UV–Vis spectrum shows a wide optical transmittance in the visible region and the obtained lower cut off wavelength is around 252 nm. The presence of 0.31 mg of cadmium element per litre of water was measured by AAS analysis which indicates the effect of dopant in the material. TG/DTA study reveals that the organic complex has slightly more stable than the semiorganic complex and it has high thermal stability of about 193 °C. Vickers microhardness tester confirms the reverse indentation size effect of the crystals and found that the crystals belongs to soft material category by Meyer law. Dielectric study was carried out on the grown crystals which represent the lower value of dielectric constant while increase the frequency.

A study of the structural and morphological properties of Ni–ferrite, Zn–ferrite and Ni–Zn–ferrites functionalized with starch

Zinc–ferrite, nickel–ferrite and mixed nickel–zinc ferrites were successfully synthesized via the thermal decomposition method from acetylacetonate complexes. To control the particle size and enhance dispersibility in an aqueous medium, starch, a natural and biocompatible compound, was used for the first time for coating such magnetic powders. X-ray powder diffraction (XRPD) was performed to study the structural properties of all samples. The presence of a single-phase spinel structure as well as the cation distribution in both sites of all investigated magnetic powders was confirmed. The values of unit cell parameters obtained from the results of the Rietveld analysis decreased, while the average crystallite size increased with increasing Ni2+ content. The average microstrain parameters unambiguously showed a change in the spinel structure with cation distribution. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) analyses were also utilized to characterize the synthesized materials, corroborating the XRPD data. The obtained results indicated that functionalization by starch was successfully achieved.

Bulk growth of organic non-linear optical (NLO) L-arginine 4-nitrophenolate 4-nitrophenol dihydrate (LAPP) single crystals by Sankaranarayanan–Ramasamy (SR) method

Organic non-linear optical single crystals of L-arginine 4-nitrophenolate 4-nitrophenol dihydrate (LAPP) are grown by Sankaranarayanan–Ramasamy (SR) method and slow evaporation solution technique (SEST) with the sizes of about 45 mm length, 15 mm diameter and 6 × 5 × 5 mm3, respectively. The grown crystals were characterised by single crystal X-ray diffraction to determine the crystallographic unit cell parameter values. The etch pit density of SEST and SR method grown LAPP crystals have been calculated using chemical etching analysis. The mechanical and optical properties of the SEST and SR method grown LAPP crystals are studied using Vickers microhardness and UV–vis NIR measurement, respectively. Laser damage threshold analysis has been made on cut and polished SEST and SR method grown LAPP crystal of 5 mm thickness. Photoconductivity study of LAPP crystal grown by SEST and SR method reveals positive photoconductivity nature. The thermal properties of the grown crystal were carried out by thermogravimetric and differential thermal analysis. The second-harmonic generation efficiency of LAPP crystal was determined using powder Kurtz–Perry technique and it was found to be 2.3 times that of standard potassium dihydrogen phosphate material.

Photoluminescence of europium(III)-doped (YxSc1−x)2O3 nanoparticles: Linear relationship between structural and emission properties

Europium (III)-doped (YxSc1−x)2O3 nanocrystalline powders of different compositions (x=0, 0.25, 0.5, 0.75 and 1) are synthesized using a polymer complex solution method. Comparative structural and optical characterization is carried out with powder X-ray diffraction and photoluminescence excitation, emission and emission decay measurements. Detailed information about unit cell parameter and energy levels of europium (III) ions are presented for all powder compositions. The second rank crystal field parameters (B02) and (B22) and crystal field strength (Nv) are calculated from the energies of Stark components of the 7F1 manifold of the europium (III) emissions. It has been shown that the crystal field parameter changes with the powder composition and shows a linear relationship with the average ionic radii of cations in the solid solutions. A similar dependence is also found for the magnitude of splitting of 7F1 manifold vs. unit cell parameter values. Moreover, this linear relationship is demonstrated for the whole family of europium (III)-doped mixed rare-earth sesquioxide hosts (RR’O3; R, R′=rare earth ions) by taking into consideration results published in the literature so far. A simple, semi-empirical equation which relates structural properties (unit cell parameters, ionic radii) of the sesquioxide host material and the emission properties of europium (III) ions (energy splitting of the 7F1 manifold, crystal field parameters and crystal field strength) are presented.

First-principle study of structural and mechanical properties of hexagonal polytypes of diamond

The values of unit-cell parameters; C-C bond lengths; elastic constants c ij and s ij ; elastic moduli B, G, and E; and hardnesses and cohesion energies have been calculated for hexagonal diamond polytypes 2H, 4H, 6H, and 8H within the approximation of density functional theory. The anisotropy of elastic moduli and hardness is investigated. It is found that the linear compressibility and hardness of polytypes in the basal plane exceeds that along the hexagonal c axis. It is shown that the difference in the anisotropic properties along and perpendicular to the hexagonal axis may be related to the specific features of polytype structure.

X-ray diffraction, spectroscopic and mechanical studies on potential organic NLO materials of metaNitroaniline and N-3-Nitrophenyl Acetamide single crystals

In the present paper, attempts were made to grow good quality metaNitroaniline (mNA) and N-3-Nitrophenyl (3-NAA) single crystals. The lattice parameter values from the Powder X-ray diffraction pattern confirms that mNA belongs to orthorhombic crystal system with the unit cell parameter values of a = 6.501 Å, b = 19.330 Å and c = 5.082 Å with space group Pbc21. Similarly the powder XRD data indicates that 3-NAA crystal retained its monoclinic structure with lattice parameter values a = 9.762 Å, b =13.287 Å, c =13.226 Å, and β = 102.99°. Investigation has been carried out to assign the vibrational frequencies of the grown crystals by Fourier Transform infrared spectroscopy technique. The SHG efficiency of mNA and 3NAA was determined by Kurtz and Perry powder technique. The Optical absorption study confirms the suitability of the crystals for device applications. The mechanical properties of the grown crystals have been studied using Vickers microhardness tester.

Investigation on solid solubility and magnetism of the non-stoichiometric compound Fe3Se4

In order to complete the research on the Fe–Se binary system, the phase structures with selenium contents from 50 to 60 at.% have been studied. Fe–Se binary samples used in this study were prepared by the high-temperature solid-state reaction method, and the phase structure of each sample was determined by powder X-ray diffraction. The solid solubility of the Fe3Se4 phase was determined to be from 56.1 to 57.6 at.% Se based on the values of unit-cell parameters. Magnetic properties of the samples were also studied.

Phase composition of Bi2O3 specimens doped with Ti, Zr and Hf

Powder mixtures of ?-Bi2O3 containing 2, 5 and 10 mole % of TiO2, ZrO2 or HfO2 were homogenized, heated at 820?C for 24 h and quenched in air. X-ray powder diffraction technique was used to characterize the prepared samples. In all cases metastable Bi2O3 polymorphs, ?-Bi2O3 or ?-Bi2O3, are found as single or major phases. Addition of Ti4+ ions stabilizes ?-Bi2O3 polymorph, while either Zr4+ or Hf4+ ions stabilize ?-Bi2O3 polymorph. In the samples with 2 and 5 mole % of TiO2 the presence of even two ?-Bi2O3 phases (Bi12TiO20 compound and a very low Ti-doped ?-Bi2O3) was established. Similarly, in the sample with 2 mole % of HfO2 two ?-Bi2O3 phases were found. Phase composition of prepared samples, values of unit cell parameters and the appearance of two polymorphs with identical crystal structure but different unit cell parameters are discussed and compared with known data.

Investigation of W2B and β-WB high-temperature phases in coatings produced by a shaped charge explosion

Coatings containing high-temperature phases of tungsten borides W2B and β-WB are obtained on titanium and steel targets by a shaped charge explosion. In some regions of the target, microhardness achieves ≥42 GPa. The phase composition of different regions of the coatings is examined by X-ray diffraction. The values of unit cell parameters indicate the formation of phases with variable composition. The crystal structure of β-WB is refined.

Anomalous phase composition in the two-phase region of DyFe3−xAlx (x≤1.0)

The structure transitions and phase relationships of DyFe3−xAlx compounds have been investigated by X-ray powder diffraction. Our XRD results show that each of the compounds with x≤0.45 crystallizes in the rhombohedral PuNi3-type structure with space group R3¯m and Z=9; for the 0.8≤x<1.0 compounds, each has a hexagonal structure of the CeNi3 type with space group P63/mmc and Z=6; and each of the samples with 0.45<x<0.8 is a two-phase mixture of the PuNi3- and CeNi3-type structures. The calculated XRD intensities of the DyFe3−xAlx compounds with x=0.2, 0.33, 0.4, and 0.45 indicate that Dy occupies the 3a and 6c sites, Fe and Al distribute randomly on the 18h site, and the 3b and 6c sites are exclusively occupied by Fe, which agrees well with those of our experimental XRD patterns. The XRD intensities of the DyFe3−xAlx compounds with x=0.8 and 1.0 have also been calculated and found to agree with the experimental results with Dy on the 2c and 4f sites, Fe and Al at the 12k site, and Fe at the 2a, 2b, and 2d sites. In the two-phase region with x=0.45–0.8, the values of unit-cell parameters and phase compositions are linearly dependent on the value of x, indicating that the two phases are constituted by the same composition x with different stacking arrangements. This abnormal two-phase equilibrium is further confirmed by the structural analysis of the DyFe2.33Al0.67 (or x=0.67) sample. The samples with x=1.1 and 1.2 were also analyzed, and each found to be a mixture of more than two phases.

Preparation and crystal structure characterization of CuNiGaSe3 and CuNiInSe3 quaternary compounds

Samples of the quaternary chalcogenide compounds, CuNiGaSe3 and CuNiInSe3, prepared by direct fusion and annealing method, were characterized by X-ray powder diffraction. In each case, the crystal structure was refined using the Rietveld method. Both compounds were found to crystallize in the tetragonal system, space group P \( \bar 4 \)2c (N°112), with unit cell parameter values a = 5.6213(1) Å, c = 11.0282(3) Å, V = 348.48(1) Å3 and a = 5.7857(2) Å, c = 11.6287(5) Å, V = 389.26(3) Å3 for CuNiGaSe3 and CuNiInSe3, respectively. These compounds have a normal adamantane structures and are isostructural with CuFeInSe3.

Synthesis, growth and studies of undoped and sodium chloride-doped Zinc Tris-thiourea Sulphate (ZTS) single crystals

Single crystals of undoped (pure) and sodium chloride (NaCl)-doped Zinc Tris-thiourea Sulphate (ZTS) were grown from aqueous solutions by slow evaporation technique. Morphological alterations have been observed when NaCl is doped into ZTS crystals. Density of the grown crystals was measured by floatation method. The values of unit cell parameters from single crystal X-ray diffraction (XRD) studies show that pure and sodium chloride-doped ZTS crystals are in orthorhombic structure. Impurity concentration in the doped crystals was estimated by using an atomic absorption spectrometer. Second Harmonic Generation (SHG) test for the undoped and NaCl-doped ZTS crystals was performed by the powder technique of Kurtz and Perry using a pulsed Nd:YAG laser. Microhardness studies show that hardness number ( H v ) increases with load for all the grown crystals of this work. From the values of work hardening coefficients, it is concluded that pure and sodium chloride-doped ZTS crystals belong to the category of soft materials. UV–vis–NIR spectra show that the grown crystals have wide optical transparency in the entire visible region. Birefringence studies of the grown samples have been performed by channelled spectrum method. The thermal stability of the materials is found to be increasing with the doping concentration of sodium chloride (NaCl) in the lattice of ZTS crystals.

Synthesis and characterization of Cu3TaIn3Se7 and CuTa2InTe4

AbstractPolycrystalline samples of Cu3TaIn3Se7 and CuTa2InTe4 were synthesized by the usual melt and anneal technique. X‐ray powder diffraction showed a single phase behavior for both samples with tetragonal symmetry and unit cell parameter values a = 5.794 ± 0.002 Å, c = 11.66 ± 0.01 Å, c /a = 2.01, V = 391 ± 1 Å3 and a = 6.193 ± 0.001 Å, c = 12.400 ± 0.002 Å, c /a = 2.00, V = 475 ± 1 Å3, respectively. Differential thermal analysis (DTA) measurements suggested a complicated behavior near the melting point with several thermal transitions observed in the heating and cooling runs. From the shape of the DTA peaks it was deduced that the melting is incongruent for both materials. Magnetic susceptibility measurements (zero‐field cooling and field cooling) indicated an antiferromagnetic character with transition temperatures of T = 70 K (Cu3TaIn3Se7) and 42 K (CuTa2InTe4). A spin–glass transition was observed in Cu3TaIn3Se7 with Tf ≈ 50 K. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Determination of the Crystal Structure of Isotacticcis-1,4-Poly(1,3-hexadiene) by X-Ray Diffraction and Molecular Mechanics

The crystal structure of isotactic cis-1,4-poly(1,3-hexadiene) has been determined through a combination of X-ray diffraction analysis and molecular mechanics. Two reasonable values for unit cell parameters were obtained from the fiber diffraction pattern of a well-oriented sample. Energy maps performed on a molecular model of the polymer chain yielded an absolute minimum corresponding to a conformation having the internal parameters similar to those of an s(2/1) helical polymer chain. Packing energy minimizations performed for all the orthorhombic and monoclinic space groups having crystallographic s(2/1) chain symmetry indicate unequivocally that the best mode of packing is obtained for a crystal structure characterized by a unit cell with parameters a = 8.98 A, b=7.82 A, and c=8.10 A in the P2 1 2 1 2 1 space group. The calculated powder and fiber diffraction patterns of this structural model are in very good agreement with the experimental diffraction patterns. Similarities and differences with the crystal structures of isotactic cis-1,4-poly(1,3-pentadiene) and isotactic cis-1,4-poly(2-methyl-1,3-pentadiene) are discussed.