Unit Cell Parameters Of Crystals Research Articles

Study of the anisotropy of α-<sup>33</sup>S single crystal thermal expansion

A technique for arbitrary symmetry crystals unit cell parameters refining on modern single-crystal diffractometers is described. The technique is based on the 2D detector position calibration. The elementary orthorhombic unit cell parameters of the α-33S single crystal have been refined. The anisotropy of parameters changes in the range of 90–350 K has been studied. It is shown that the relative increase in parameter c is 6.4%. The obtained dependences are approximated by second–third degree polynomials. The absolute increase in cell volume is 138.4 A3, and the relative increase is 4.3%. The temperature dependencies of the thermal expansion tensor elements has been refined. The coefficients of α-33S thermal expansion tensor at the room temperature are: α11 = 15.35 × 10–5, α22 = 8.56 × 10–5, α33 = 9.12 × 10–5 К–1.

Orientational and crystallographic relationships in thin films of yttrium orthoferrite on sapphire substrates.

An algorithm is proposed for determining the orientational relationships and crystal unit-cell parameters of thin films using a laboratory X-ray diffractometer and stereographic projections. It is illustrated by the treatment of experimental data obtained for yttrium orthoferrite YFeO3 films on single crystalline sapphire (Al2O3) substrates for film thicknesses in the range from 100 to 7000 Å. Precise determination of unit-cell constants and angles is possible by combining the results of X-ray measurements made in the in-plane and out-of-plane geometries. The unit-cell unit parameters and orientation relationships for thin films were determined. For the studied films, typical errors in determining unit-cell parameters and angles are better than 0.17 Å and 0.17°, respectively.

Phase Equilibria in the Cu2Se–Cu8SiSe6–Cu8GeSe6 System

Phase equilibria in the Cu2Se–Cu8SiSe6–Cu8GeSe6 area of the Cu2Se–SiSe2–GeSe2 system have been studied using differential thermal analysis (DTA), X-ray powder diffraction analysis (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDX). The results served to plot a Т–х diagram of the Cu8SiSe6–Cu8GeSe6 boundary system, a series of polythermal sections, and a 300-K isothermal section of the phase diagram and a liquidus surface projection for the title system. The primary crystallization and homogeneity fields of phases, and the characters and temperatures of invariant and monovariant equilibria have been determined. In the Cu8SiSe6–Cu8GeSe6 boundary system, continuous solid solutions have been found to exist between the high-temperature phases of the terminal compounds and extensive homogeneity area based on their low-temperature phases were found. The crystal lattice types and unit cell parameters have been determined for the terminal compounds and both phases of solid solutions using X-ray powder diffraction data. The prepared phases of variable composition are of interest as environmentally friendly functional materials.

Silver-substituted hydroxyapatite: Mechanochemical synthesis and thermal stability

Silver-substituted hydroxyapatites have been prepared by the mechanochemical method in a planetary ball mill. In order to prepare a series of samples of the Ca10−xAgx (PO4)6(OH)2−x composition, the concentration of silver was varied in the range x = 0–2. The resultant samples were characterized by means of X-ray diffraction, FTIR spectroscopy, and simultaneous thermal analysis. It was shown that the single-phase substituted hydroxyapatites were achieved with silver concentrations of up to х = 1.5. An increase in the concentration of silver results in an increase in the volume and the unit-cell parameters of crystals. At a concentration x of 2.0, the sample contains an impurity phase of silver phosphate. The thermal stability of the as-synthesized silver-substituted samples was shown to directly depend on the degree of substitution of calcium cations by silver cations. The decomposition temperature decreases as the degree of substitution increases. Upon heating of the substituted samples, silver is gradually released from hydroxyapatite with the formation of a metallic nanosized silver phase, followed by the structural transformation of the hydroxyapatite lattice into silver-substituted tricalcium phosphate at a higher temperature. In this case, the introduction of silver cations results in a decrease in the values of the lattice parameters of tricalcium phosphate, showing a non-linear dependence on the silver concentration.

Biomineralization of mantis shrimp dactyl club following molting: Apatite formation and brominated organic components

The stomatopod Odontodactylus scyllarus uses weaponized club-like appendages to attack its prey. These clubs are made of apatite, chitin, amorphous calcium carbonate, and amorphous calcium phosphate organized in a highly hierarchical structure with multiple regions and layers. We follow the development of the biomineralized club as a function of time using clubs harvested at specific times since molting. The clubs are investigated using a broad suite of techniques to unravel the biomineralization history of the clubs. Nano focus synchrotron x-ray diffraction and x-ray fluorescence experiments reveal that the club structure is more organized with more sub-regions than previously thought. The recently discovered impact surface has crystallites in a different size and orientation than those in the impact region. The crystal unit cell parameters vary to a large degree across individual samples, which indicates a spatial variation in the degree of chemical substitution. Energy dispersive spectroscopy and Raman spectroscopy show that this variation cannot be explained by carbonation and fluoridation of the lattice alone. X-ray fluorescence and mass spectroscopy show that the impact surface is coated with a thin membrane rich in bromine that forms at very initial stages of club formation. Proteomic studies show that a fraction of the club mineralization protein-1 has brominated tyrosine suggesting that bromination of club proteins at the club surface is an integral component of the club design. Taken together, the data unravel the spatio-temporal changes in biomineral structure during club formation. Statement of significanceMantis shrimp hunt using club-like appendages that contain apatite, chitin, amorphous calcium carbonate, and amorphous calcium phosphate ordered in a highly hierarchical structure. To understand the formation process of the club we analyze clubs harvested at specific times since molting thereby constructing a club formation map. By combining several methods ranging from position resolved synchrotron X-ray diffraction to proteomics, we reveal that clubs form from an organic membrane with brominated protein and that crystalline apatite phases are present from the very onset of club formation and grow in relative importance over time. This reveals a complex biomineralization process leading to these fascinating biomineralized tools.

Investigation on growth, crystal structure, third-order optical nonlinearity properties and DFT computational studies of novel proton transfer 3-aminopyridine P-nitrobenzoate P-nitrobenzoic acid (3APPNB) single crystal for third-order NLO applications

A new organic single crystal of 3-aminopyridine p-nitrobenzoate p-nitrobenzoic acid (3APPNB) with a size of 8 × 4 × 2 mm3 was grown by slow evaporation solution growth technique at room temperature using methanol solvent. The lattice parameter values were evaluated with the help of single crystal XRD and it confirms that the 3APPNB crystal belongs to triclinic crystal structure and the space group P-1. Crystal unit cell parameters are a = 9.3384(5) Å, b = 10.0403(5) Å, c = 11.094(6) Å, α = 109.4940(10)°, β = 93.964(2)°, γ = 99.890(2)° and V = 957.03 (9) (Å3) were determined. The 3APPNB crystal crystallizes in a centrosymmetric nature, triclinic system and space group P-1. SCXRD study shows that both the anion and the cation are interlinked to each other by two types of symmetrical intermolecular C–H…O and N–H···O hydrogen bonds. The crystalline nature and hkl phases have been determined using Powder XRD studies. The presence of different vibrational groups in the 3APPNB compound is examined by employing Fourier transform infrared (FT-IR) spectral analysis. UV–Vis-DRS spectral analysis signifies that the 3APPNB has a wide transmittance (98 %) and a cut-off wavelength of around 317 nm. The etch pit density (EDP) of 3APPNB crystal was examined by a chemical etching analysis. The thermal studies expose that 3APPNB is thermally stable up to 172 °C. The surface morphology of the 3APPNB is analyzed by SEM. The nonlinear properties like β, n2 and χ(3) were measured through the Z-scan analysis and the values were calculated to be 5.78 × 10−5 m/W, 8.05 × 10−12 m2/W) and χ(3) = 8.936 × 10−9. The third-order nonlinear optical (TONLO) χ(3) values are higher. The achieved TONLO χ(3) value when compared to other similar constituents is owing to the tarnish movement of π-electron configuration from the donor to an acceptor that makes the molecules highly polarized. The results reveal that the 3APPNB crystal finds applications in devices like optical switching and optical limiting. The quantum-chemical theoretical analyses are performed to measure the intrinsic properties of the 3APPNB molecules using DFT calculation. The band gap, orbital energy and second hyperpolarizability are also studied using changing the applied field. Furthermore, Quantum chemical calculations are used to obtain the MESP, HOMO-LUMO and first-order hyperpolarizability for the 3APPNB compound.

Crystal Structure L-Asparagine Potassium Nitrate Single Crystals

The elemental analysis of the compound confirms the ratio of the compound. The sharp and well defined Bragg peaks obtained in the powder X-ray diffraction pattern confirm the crystalline nature of the compound. The single crystal unit cell parameters of the compound show that the grown crystal belongs to orthorhombic system with space group P. The optical property of the compound was ascertained through UV-visible spectral analysis. The various characteristics absorption bands in the compound were assigned through Fourier transform infra-red (FTIR) spectroscopy. Thenonlinear optical property study indicates that the compound has SHG efficiency 0.50 times greater than that of standard potassium dihydrogen phosphate (KDP).

Noncentrosymmetric Supramolecular Hydrogen-Bonded Assemblies Based on Achiral Pyrazine-Bridged Zinc(II) Coordination Polymers with Pyrazinedione Derivatives

Reaction of M(OAc)2·xH2O (M, x = Zn, 2 and Co, 4), 1,4-dihydro-5,6-dicyano-2,3-pyrazinedione (H2CN2pyzdione), and pyrazine (pyz) affords two compounds of the same molecular formula {[M(H2O)6][M(CN2pyzdione)2(pyz)]·6H2O}n (M = Zn for 1 and Co for 2) in which discrete units of [M(H2O)6]2+ are linked to one-dimensional chains of [M(CN2pyzdione)2(pyz)]2– via multiple O–H···O hydrogen-bonding interactions and M2+-bound H2O molecules in [M(H2O)6]2+ also serve as linkers of hydrogen-bonded interstitial H2O molecules. Remarkably, 1 crystallizes in the monoclinic crystal system, the similar crystal system and unit cell parameters as 2, but with a space group distinct from 1 and 2, i.e., 1 is the noncentrosymmetric space group C2, whereas 2 is the centrosymmetric space group C2/m. This polar structure for 1 is induced by the presence of alternating arrangements of distinguishable two axial Zn–N bonds within [Zn(CN2pyzdione)2(pyz)]2– chains. Indeed, solid-state circular dichroism spectra of 1 exhibit significant Cotton effects, as evidenced by the polar space group C2. Moreover, these Cotton effects show clear temperature-dependence depending on contents of H2O molecules of 1.

ОПРЕДЕЛЕНИЕ ПАРАМЕТРОВ УРАВНЕНИЯ СОСТОЯНИЯ МОЛЕКУЛЯРНЫХ КРИСТАЛЛОВ НА ОСНОВЕ ДИФРАКТОМЕТРИЧЕСКИХ ИССЛЕДОВАНИЙ

The paper presents the results of determining the crystal structure of PETN, hexogen, and HMX samples by X-ray diffractometry and calculations of the unit cell parameters of molecular crystals associated with the processing of X-ray diffractometry results, and experimental relationships between the unit cell volumes of molecular crystals on temperature. The obtained experimental data on the isobaric compression and expansion of the studied molecular crystals allowed us to specify the thermal component of the equations of the state of molecular crystals and obtain an expression for the isobaric thermal expansion coefficient associated with the mathematical model of the thermal component of the equations of state of molecular crystals. The obtained analytical dependence of the isobaric coefficient of thermal expansion on the temperature of the considered samples correctly describes the limiting transition to low temperatures. We propose a method of approximation for the obtained experimental relationships between temperature and the unit cell volume of the studied substances under isobaric compression/expansion based on a mathematical model of the semi-empirical equations of state of molecular crystals. This approach allowed us to obtain analytical relationships between the crystal unit cell volume and temperature, which describes the results of X-ray diffractometry of the molecular crystal samples considered in the work with an accuracy of up to 3 %.

Resolving the structure of V3O7·H2O and Mo-substituted V3O7·H2O.

Vanadate compounds, such as V3O7·H2O, are of high interest due to their versatile applications as electrode material for metal-ion batteries. In particular, V3O7·H2O can insert different ions such as Li+, Na+, K+, Mg2+ and Zn2+. In that case, well resolved crystal structure data, such as crystal unit-cell parameters and atom positions, are needed in order to determine the structural information of the inserted ions in the V3O7·H2O structure. In this work, fundamental crystallographic parameters, i.e. atomic displacement parameters, are determined for the atoms in the V3O7·H2O structure. Furthermore, vanadium ions were substituted by molybdenum in the V3O7·H2O structure [(V2.85Mo0.15)O7·H2O] and the crystallographic positions of the molybdenum ions and their oxidation state are elucidated.

Precisely control the ultraviolet to blue light conversion for plant growth: Rigid crystal structure, lattice substitution and flux effect in the Ca1.1Sr0.9SiO4:Ce3+, Li+ phosphor

A series of Ce3+-doped Ca1.1Sr0.9SiO4-based phosphors has led to the development of a fingerprint spectrum to precisely tune the UV to blue light conversion for application in the photosynthesis of different plants in agriculture. The addition of MX2 flux (M = Ca, Ba; X = Cl, Br) not only remarkably enhances the luminescence efficiency, but also fine tunes the photoluminescence (PL) wavelength and photoluminescent excitation (PLE) peaks. With increasing Al content doping in the Si site, the excitation and emission peaks of the Ca1.08Sr0.88Si1-zAlzO4:0.02Ce3+,0.02Li+,0.04CaCl2 (CSSA:CeLiCaCl) phosphor shift to longer wavelengths, i.e. from 367 (z = 0) to 373 (z = 0.04) nm and from 429 (z = 0) to 448 (z = 0.04) nm, respectively, along with an increase of the luminescence intensity. Rietveld refinement of the XRD data for Ca2-ySrySiO4 (y = 0.8, 0.9, 1.0) revealed that Ca1.1Sr0.9SiO4 has the highest rigidity, which can be correlated with the shortest Si-O bond length and strongest bond energy along the series. The crystal structure and unit cell parameters of CSSA:CeLiCaCl (z = 0, 0.03 and 0.05) were also obtained, revealing that the efficient and tunable blue emission of the CSSA:CeLiCaCl phosphors can be attributed to the crystal structure distortions induced by the [(Si/ Al)O4] tetrahedron, while high rigidity is maintained. The combined effects of the Si4+ substitution by Al3+ and flux addition on the crystal structure and luminescence properties of the Ce3+-doped Ca1.1Sr0.9SiO4 phosphors are discussed in detail.

Optoelectronic, luminescence, and nonlinear properties of a non-centrosymmetric Cd(II)-based complex

Single crystals of 1,2-diammoniumcyclohexane tetrabromocadmate(II) monohydrate, abbreviated as CdDACH, have been obtained by the slow evaporation solution growth method using methanol as solvent. Single-crystal X-ray diffraction analysis has been utilized to compute the unit cell parameters of the CdDACH crystal. The molecular structure has been analyzed by FTIR, FT-Raman, and ATG/DSC measurements. The electronic behavior has been determined by DFT methods at the B3LYP/LANL2DZ level. The UV/Visible spectrum indicates a direct band gap (4.88 eV) and a low cut-off wavelength (250 nm) for the crystal. Photoluminescence measurement of CdDACH yielded a broad peak at 506 nm with a width at half-maximum of 94 nm. Electrical and optical parameters, namely refractive index (n), extinction coefficient (k), electrical conductivity (σe), and optical conductivity (σopt), have been derived by means of diffuse-reflectance spectroscopy. With a high optical conductivity of 1010 s−1, the suitability of the photo-response of the crystal for use in devices that perform information processing has been established. The first hyperpolarizability (β) and second hyperpolarizability (γ) of the material have been theoretically investigated through TD-DFT calculations. The third-order susceptibility χ(3) of CdDACH crystals, estimated by the Lorentz approximation, was found to be of the order of 10−4 esu. The obtained results indicate that CdDACH may be adopted for future second and third harmonic generation applications.

Synthesis, X-ray Structure, Conformational Analysis, and DFT Studies of a Giant s-Triazine bis-Schiff Base

The current work involves the synthesis of 2,2′-(6-(piperidin-1-yl)-1,3,5-triazine-2,4-diyl)bis(hydrazin-2-yl-1-ylidene))bis(methanylylidene))diphenol 4, characterization, and the DFT studies of the reported compound. The crystal unit cell parameters of 4 are a = 8.1139(2) Å, b = 11.2637(2) Å, c = 45.7836(8) Å. The unit cell volume is 4184.28(15) Å3 and Z = 4. It crystallized in the orthorhombic crystal system and Pbca space group. The O…H, N…H, C…H, H…H and C…C intermolecular contacts which affect the crystal stability were quantitatively analyzed using Hirshfeld calculations. Their percentages were calculated to be 9.8, 15.8, 23.7, 46.4, and 1.6% from the whole contacts occurred in the crystal, respectively. Conformational analysis was performed using DFT calculations for 17 suggested conformers and the most stable conformer was found to be the one which is stabilized by two intramolecular O-H…N hydrogen bonding interactions. This conclusion was further revealed by natural bond orbital calculations.

Crystal growth, physico-chemical and quantum chemical investigations on Butyl para-hydroxybenzoate single crystals for optical applications

The organic third-order nonlinear optical material of Butyl para-hydroxybenzoate (BHB) crystal is grown by the solvent evaporative method. The structure and unit cell parameters of BHB crystal are analyzed by the single-crystal XRD. The transmittance and absorption spectra of BHB crystal are assessed by UV–vis. spectrometer with the wavelength range of 200 to 1200 nm. Using the optical assessment the different optical constant values like extinction and absorption coefficient, optical energy bandgap and refractive index were estimated. The laser induced damage threshold nature is evaluated. The third-order nonlinear optical properties like absorption coefficient, third-order susceptibility and refractive index value are evaluated using the z-scan technique. From density functional theory, first-order hyperpolarizability, Mulliken atomic charge population, bonding interactions among the orbits were examined. The intermolecular bonding interactions of BHB crystal were quantitatively examined by using the Hirshfeld surface and 2D fingerprint analysis. Also, the various vibtational analyses were obtained and discussed.

Microhardness and SHG efficiency of pure and picric acid-added KDP crystals

Pure and picric acid-added KDP (potassium dihydrogen phosphate) crystals are grown by slow evaporation technique from aqueous solution. Unit cell parameters for pure and doped KDP crystals were measured from single-crystal X-ray diffraction studies. Vickers and Knoop microhardness studies were carried out on the grown crystals over a load range of 0.1 to 0.5 N. The microhardness decreases with load P, i.e., normal indentation size effect (ISE), and from Meyers index it is shown that grown crystals falls in to hard material category. Mechanical properties, such as Young’s modulus, yield strength, elastic stiffness constant, were calculated for pure and doped KDP crystals. Hardness anisotropy has been observed in accordance with the orientation of the crystal. Etching studies were carried out using aqueous solution as an etchant. Improved second-harmonic generation efficiency is observed for doped KDP crystals in comparison to pure KDP crystals.

Crystal Structure of the Pneumococcal Vancomycin-Resistance Response Regulator DNA-Binding Domain

Vancomycin response regulator (VncR) is a pneumococcal response regulator of the VncRS two-component signal transduction system (TCS) of Streptococcus pneumoniae. VncRS regulates bacterial autolysis and vancomycin resistance. VncR contains two different functional domains, the N-terminal receiver domain and C-terminal effector domain. Here, we investigated VncR C-terminal DNA binding domain (VncRc) structure using a crystallization approach. Crystallization was performed using the micro-batch method. The crystals diffracted to a 1.964 Å resolution and belonged to space group P212121. The crystal unit-cell parameters were a = 25.71 Å, b = 52.97 Å, and c = 60.61 Å. The structure of VncRc had a helix-turn-helix motif highly similar to the response regulator PhoB of Escherichia coli. In isothermal titration calorimetry and size exclusion chromatography results, VncR formed a complex with VncS, a sensor histidine kinase of pneumococcal TCS. Determination of VncR structure will provide insight into the mechanism by how VncR binds to target genes.

Methyl 4-aminobenzoate (MAB) single crystal grown by Bridgman - Stockbarger method for optical applications

Abstract Methyl 4-aminobenzoate (MAB) single crystal has been grown by Bridgman-Stockbarger method with suitable temperature gradient. Unit cell parameters of MAB single crystal have been determined from X-ray diffraction analysis. The different types of vibration mode were analysed through the FTIR spectral study. UV–Visible NIR spectrum shows that the grown crystal possesses good optical transmittance of about 80% in the infrared region. The obtained transmittance data have been used to evaluate the various optical properties such as optical absorption coefficient, bandgap, refractive index and extinction coefficient of the grown crystal. The detailed thermal properties of the MAB single crystal have been examined through the simultaneous thermogravimetric and differential thermal analyses. The laser damage threshold analysis reveals the good resistance of MAB single crystal to high power laser radiation compared to several known nonlinear optical crystals. Third-order nonlinear behavior of MAB crystal was analysed by open and closed aperture Z-scan analysis.

Study of Bursa L6 ordinary chondrite by X‐ray diffraction, magnetization measurements, and Mössbauer spectroscopy

AbstractWe report the results of the complex study of the bulk interior of Bursa L6 ordinary chondrite using optical microscopy, scanning electron microscopy with energy dispersive spectroscopy, electron microprobe analysis (EMPA), X‐ray diffraction (XRD), magnetization measurements, and Mössbauer spectroscopy. The main and minor iron‐bearing phases and their chemical compositions were determined by these techniques. The detected iron‐bearing phases in the bulk interior of Bursa L6 are the following: olivine; orthopyroxene; Ca‐rich clinopyroxene; troilite; chromite; hercynite; ilmenite; the α2‐Fe(Ni, Co), α‐Fe(Ni, Co), and γ‐Fe(Ni, Co) phases; and ferrihydrite resulting from meteorite terrestrial weathering. Using the EMPA, the values of fayalite and ferrosilite were obtained as ~25.2% and ~21.4%, respectively. The unit cell parameters for silicate crystals were determined from XRD, then the Fe2+ and Mg2+ occupations of the M1 and M2 sites in these crystals were estimated. Further calculations of the ratios of the Fe2+ occupancies in the M1 and M2 sites in olivine and orthopyroxene based on XRD and Mössbauer spectroscopy appeared to be in a good agreement. The temperatures of equilibrium cation distributions for olivine and orthopyroxene obtained from these techniques are consistent: 623 K (XRD) and 625 K (Mössbauer spectroscopy) for olivine and 1138 K (XRD) and 1122 K (Mössbauer spectroscopy) for orthopyroxene.

Synthesis, Characterization, Photoluminescence and Piezoelectric Study of Dy1.98Yb0.02Ti2O7 and Lu1.98Er0.02Ti2O7

Dy1.98Yb0.02Ti2O7 and Lu1.98Er0.02Ti2O7 with the cubic pyrochlore structure were prepared at 1050 °C and 1400 °C using solid state reaction method. The crystal structure and unit cell parameters of powder samples were determined by X-ray diffraction method (XRD). Using TG/DTA thermal analysis, we determined the thermal behaviours of starting materials and Curie temperature of fine samples. Dy1.98Yb0.02Ti2O7 and Lu1.98Er0.02Ti2O7 have high Curie temperature at 770 °C and 765 °C, respectively. To determine morphological structure, elemental composition, photoluminescence properties, dielectric constant, loss tangent, and piezoelectric charge constant of Dy1.98Yb0.02Ti2O7 and Lu1.98Er0.02Ti2O7, scanning electron microscope (SEM), photoluminescence spectrophotometer (PL), LCR-meter and d33-meter were used. The results show that Dy1.98Yb0.02Ti2O7 and Lu1.98Er0.02Ti2O7 are multifunctional materials which show both photoluminescence properties and piezoelectric properties.

Characterization of the matrix and fusion crust of the recent meteorite fall Ozerki L6

AbstractWe studied the interior and the fusion crust of the recently recovered Ozerki L6 meteorite using optical microscopy, scanning electron microscopy (SEM) with energy dispersive spectroscopy, X‐ray diffraction (XRD), magnetization measurements, and Mössbauer spectroscopy. The phase composition of the interior and of the fusion crust was determined by means of SEM, XRD, and Mössbauer spectroscopy. The unit cell parameters for silicate crystals were evaluated from the X‐ray diffractograms and were found the same for the interior and the fusion crust. Magnetization measurements revealed a decrease of the saturation magnetic moment in the fusion crust due to a decrease of Fe‐Ni‐Co alloy content. Both XRD and Mössbauer spectroscopy show the presence of magnesioferrite in the fusion crust. The temperatures of cation equilibrium distribution between the M1 and M2 sites in silicates calculated using the data obtained from XRD and Mössbauer spectroscopy appeared to be in a good consistency: 553 and 479 K for olivine and 1213 and 1202 K for orthopyroxene.