Crystal Cell Parameters Research Articles

Microporous Metal-Organic Framework Based on a Bifunctional Linker for Selective Sorption of CO2 over N2 and CH4.

A bifunctional organic linker 4-(4-carboxyphenyl)-1,2,4-triazole (HCPT), incorporating both carboxylate and triazole groups, has been successfully used in the construction of a 2-fold interpenetrated dynamic metal-organic framework (MOF), {[Cu3(CPT)4(μ3-OH)]·NO3·7H2O·EtOH}n (1) based on a triangular Cu(II)-hydroxo cluster as secondary building unit (SBU). Upon solvation/desolvation and temperature, the crystal cell parameters of 1 could be fine-tuned. More importantly, a transformation from disordered phase to a more ordered phase after activation was observed via a single-crystal-to-single-crystal mode. Gas sorption studies reveal that the activated 1 exhibits highly selective sorption of CO2 over N2 and CH4 at room temperature.

Influence of chemical substitution on the photoluminescence of Sr(1−x)PbxWO4 solid solution

The solid solution Sr1−xPbxWO4 based on luminescent tungstates SrWO4 and PbWO4 has been synthesized by solid-state reaction for all compositions 0≤x≤1. Using Rietveld method, the structural data of all polycrystalline samples have been refined and crystal cell parameters exhibited a linear behavior as a function of x. All substituted structures are of scheelite type. Scanning electron microscopy showed that a high level of crystallization characterized the samples, with modifications in sizes and shapes depending on composition x. Infrared and Raman spectroscopy have been performed to characterize the evolution of vibrational modes with substitution rate. Finally, a systematic study of luminescence under X-ray excitation has been performed: in the composition range x=0.2 to 0.4, intensities of emission exhibited increased values. The luminescence profiles have been interpreted in terms of four Gaussian components, two of them depending on substitution rate.

Mechanism of the formation of micropores in the thermal decomposition of goethite to hematite

The mechanisms of the formation of micropores in the thermal decomposition of goethite to hematite have been studied through the measurements of X-ray diffraction, Brunauer–Emmett–Teller adsorption and scanning electronic microscopy, as well as the estimation of crystal cell parameters in this work. The results have shown that the thermal decomposition led to the crystal cells of goethite to be contracted along the [010] and [001] directions and to be elongated along the [100] direction, forming nano-scale and rod-like hematite. It was the contractions along the two directions that led to the formation of the micropores in the hematite particles. Copyright © 2015 John Wiley & Sons, Ltd.

Crystal growth, morphology, spectrographic characterization and thermal properties of Glycine Barium Bromo Chloride crystals

Glycine Barium Bromo Chloride material was purified by repeated recrystallization. Single crystal was grown by the slow evaporation solution technique (SEST). The presence of functional groups in the grown crystals was confirmed by Fourier transform infrared spectrum analysis. Thermal properties of the crystals were investigated using thermogravimetric (TG) and differential thermal analyses (DTA). The dielectric studies were carried out to identify the phase transition temperature and the dielectric constant was found. The transparency of crystal was tested using UV–visible spectra. Single crystal X-ray diffraction study has been carried out to find the crystal system and unit cell parameters.

Semiempirical and DFT computations of the influence of Tb(III) dopant on unit cell dimensions of cerium(III) fluoride.

Several computational methods, both semiempirical and ab initio, were used to study the influence of the amount of dopant on crystal cell dimensions of CeF3 doped with Tb(3+) ions (CeF3 :Tb(3+) ). AM1, RM1, PM3, PM6, and PM7 semiempirical parameterization models were used, while the Sparkle model was used to represent the lanthanide cations in all cases. Ab initio calculations were performed by means of GGA+U/PBE projector augmented wave density functional theory. The computational results agree well with the experimental data. According to both computation and experiment, the crystal cell parameters undergo a linear decrease with increasing amount of the dopant. The computations performed using Sparkle/PM3 and DFT methods resulted in the best agreement with the experiment with the average deviation of about 1% in both cases. Typical Sparkle/PM3 computation on a 2×2×2 supercell of CeF3:Tb3+ lasted about two orders of magnitude shorter than the DFT computation concerning a unit cell of this material.

Distribution of dopant metals between PbTiO3 crystals and PbO-B2O3 flux

Single crystals of lead titanate PbTiO3 doped with silicon, calcium, chromium, manganese, cobalt, nickel, copper, zinc, and cadmium were grown. The compositions and crystallographic parameters of the crystals were studied. The lowest distribution coefficients of dopants between PbTiO3 crystals and flux were observed with Mn +2 and Co +2 and the highest, with Ca +2 . Doping with niobium leads to the formation of solid solutions with the pyrochlore structure A2B2O7 and even higher distribution coefficient. A correlation was found between dopant concentrations and crystal cell parameters.

Raman spectra of R2O3 (R—rare earth) sesquioxides with C-type bixbyite crystal structure: A comparative study

Raman spectra of R2O3 (R—Sc, Er, Y, Ho, Gd, Eu, and Sm) powders with C-type bixbyite crystal structure are measured. With the help of these data and ones, previously published for other oxides from the same structural family, general dependencies of the frequencies of the Raman peaks on the cubic crystal unit cell parameter are constructed. Using these dependencies and knowing the symmetry of the peaks for one of the oxides, determined from previous single-crystal measurements, it is possible to find out the symmetry of the peaks from the spectra of all compounds. It was found that the frequency of the six lowest frequency peaks scales with the square root of the mass of the rare earth showing that mainly R ions take part in these vibrations. These results agree with performed here lattice dynamical calculations. The anomalous softening of the frequency of some peaks in the spectra of Eu2O3 is discussed.

Thermostimulated structural changes in C60-CCl4 and C70-CCl4 crystal solvates

The crystal solvates in C60-CCl4 and C70-CCl4 systems obtained by crystallization from CCl4 solution at room temperature were studied by IR Fourier spectroscopy and X-ray diffraction. The C70 · (CCl4)n crystal solvate was obtained and studied for the first time; its hexagonal crystal lattice has unit cell parameters a = 10.658 ± 0.001 A and c = 10.811 ± 0.002 A. The temperature ranges of its destruction were determined.

A novel Cd(II) complex with 1,3-bis(4-Pyridyl)propane: Synthesis, crystal structure, and interaction with DNA

The complex [Cd(Bpp)3Cl2]n · 2H2O (Bpp = 1,3-bis(4-pyridyl)propane) has been synthesized and characterized by elementary analysis, IR spectrum and singel-crystal X-ray diffraction. The crystal belongs to monoclinic system, space group C2/c with the crystal cell parameters of a = 31.05(3), b = 17.556(13), c = 16.281(13) Aβ = 121.402(7)°, V = 7574(10) A3, and Z = 8. The compound has formed a 1D surface shape structure through these coordinate modes with the ligand. The 2D layers are further aggregated by hydrogen bonding with octameric subunits.

Structural and optical properties of Cd1−xZnxS (0 ≤ x ≤ 0.3) nanoparticles

Cd1−xZnxS nanoparticles for Zn = 0–30 % were successfully synthesized by a conventional chemical co-precipitation method at room temperature. X-ray diffraction spectra confirmed the pure zinc blend cubic structure of undoped CdS; but Zn-doping on Cd–S matrix induced the mixed phases of cubic and hexagonal structure. The reduced crystal size, d-value, cell parameters and higher micro-strain at lower Zn concentration were due to the distortion produced by Zn2+ in Cd–S lattice. The enhancing diffraction intensity at lower Zn concentrations was due to the substitution of Zn2+ ions instead of Cd2+ ions whereas the reduced intensity after 20 % was due to the presence of Zn2+ ions both as substitutionally and interstitially in Cd–S lattice. The nominal stoichiometry and chemical purity was confirmed by energy dispersive X-ray analysis. The initial blue shift of energy gap from undoped CdS (3.75 eV) to Zn = 10 % (3.82 eV) was due to the size effect and also the incorporation of Zn2+ in the Cd–S lattice. The observed red shift of energy gap at higher Zn concentrations could be attributed to the improved crystallinity. The band gap tailoring was useful to design a suitable window material in fabrication for solar cells and other opto-electronic devices. The characteristic IR peaks around 617–619 cm−1 and the reduced intensity by Zn-doping confirmed the presence of Zn in Cd–S lattice.

Structural, vibrational and dielectric study of Ni doped spinel Co ferrites: Co1−xNixFe2O4 (x=0.0, 0.5, 1.0)

Bulk samples of spinel ferrites with the compositional formula, Co1−xNixFe2O4 (x=0.0, 0.5, 1.0) were synthesized by a solid-state reaction route to discuss doping effect on the structural, vibrational and dielectric properties. The crystal structure and cell parameters were refined by the Rietveld analysis, infers that ceramics crystallized in single-phase cubic structure with Fd-3m space group. The variation in cell parameters with Ni substitution confirmed the partial substitution of the Co3+ by Ni3+ into the spinel CoFe2O4 structure. A blue shift in Ni doped CoFe2O4 ferrite has been observed as compared to parent CoFe2O4 from Raman scattering measurements. The dielectric constant (ε′) and loss tangent (tanδ) have been investigated as a function of composition and frequency in the frequency range 10Hz–1MHz. Porous ceramics are useful for microelectronics with lower value of dielectric constant.

Synthesis pretreatment and characterization of a magnetic layered double hydroxides fluorescent probe

Abstract Using magnetic layered double hydroxide (MLDH) as carrier of fluorescein (FLU), a fluorescent composite of MLDH-FLU was prepared via intercalation reaction of ion change. The crystal properties of MLDH-FLU were investigated through XRD, IR, TEM and TG-DSC characterization. It is shown that the crystal type of MLDH-FLU composite matched well with R-hexagonal crystal system of MLDH, with crystal cell parameters of a , c and channel height h equal to 0.3199, 2.411 and 0.3267 nm respectively. The superabundant pigment adsorbed outside the composite should be cleared before interference with cells, but excessive wash would decrease stability and cause crystal phase transformation of MLDH.

Solid solutions of La-doped BiFeO3 obtained by the Pechini method with improvement in their properties

In this work, the synthesis of a series of solid solutions of Bi1−xLaxFeO3 (BLFO) (0≤x≤ 0.15) obtained by the Pechini method is reported. The effects of lanthanum concentrations on the phase formation, grain size, as well as electric and magnetic properties were studied. The XRD results displayed the single BiFeO3 (BFO) phase for the different employed compositions. Crystal structure and cell parameters were refined by the Rietveld analysis, indicating that the obtained ceramics crystallized in the rhombohedral structure. The slight variation of the cell parameters and density values confirmed the partial substitution of Bi3+ by La3+ into the perovskite A site like BiFeO3 structure. Scanning electron microscopy was used to obtain the morphology of the different synthesized compounds, revealing a diminution of the grain sizes during the sintering process, attributed to the increment of La3+ content. Electric impedance spectroscopy (EIS) measurements were performed to evaluate the electric properties, thus showing a notable increase in the permittivity. The effect of incorporating lanthanum into the BFO structure enhanced ferroelectric and ferromagnetic properties.

Structural elucidation of Pogostone and its dimers-two novel diastereomers combined with X-ray diffraction and spectroscopy

Two new dimers of Pogostone were prepared simultaneously when synthesizing Pogostone. Their molecular structures were elucidated on the basis of spectral interpretation, including FT-IR, 1H and 13C NMR, homo-nuclear correlation (COSY), and hetero-nuclear correlation (HMQC and HMBC) together with single crystal X-ray diffraction. Compound 1 crystallized in the orthorhombic P bc n space group with the crystal cell parameters a=11.24391(16) Å, b=17.7313(3) Å, c=22.6331(4) Å, V=4512.34(12) Å3 and Z=8. Compound 2 crystallized in the monoclinic P 21/c space group with the crystal cell parameters a=15.0390(4) Å, b=11.3591(3) Å, c=13.1370(3) Å, β=94.167(2)°, V=2238.25(10) Å3 and Z=4. The X-ray results demonstrated there solely existed classic H-bond intramolecular rather than intermolecular interactions in the molecules of the two compounds. Furthermore, regarding the R configuration (compound 1), two pyranone rings were approximately perpendicular to each other (100.614°), whereas for the S configuration (compound 2), two pyrone rings were almost paralleled (7.143°). It had obvious influence on the symmetry of molecule and great different spatial structure and the packing mode.

Understanding the Structure and Electronic Properties of Molecular Crystals Under Pressure: Application of Dispersion Corrected DFT to Oligoacenes

Oligoacenes form a fundamental class of polycyclic aromatic hydrocarbons (PAH) which have been extensively explored for use as organic (semi) conductors in the bulk phase and thin films. For this reason it is important to understand their electronic properties in the condensed phase. In this investigation, we use density functional theory with Tkatchenko-Scheffler dispersion correction to explore several crystalline oligoacenes (naphthalene, anthracene, tetracene, and pentacene) under pressures up to 25 GPa in an effort to uncover unique electronic/optical properties. Excellent agreement with experiment is achieved for the pressure dependence of the crystal structure unit cell parameters, densities, and intermolecular close contacts. The pressure dependence of the band gaps is investigated as well as the pressure induced phase transition of tetracene using both generalized gradient approximated and hybrid functionals. It is concluded that none of the oligoacenes investigated become conducting under elevated pressures, assuming that the molecular identity of the system is maintained.

Preparation of Strontium-Barium Hydroxyapatite by Coprecipitation

This paper reports a novel coprecipitation process for the preparation of strontium-barium hydroxyapatite [Sr5-xBax(PO4)3OH]. Strontium nitrate, barium nitrate and phosphoric acid were dissolved in water to form a homogeneous Sr-Ba-P aqueous solution. The samples were characterized by powder X ray diffraction, Fourier transformed infrared spectroscopy and scanning electron microscopy. The results showed that the barium phosphate [Ba3(PO4)2] phase appeared at the samples prepared at the pH value lower than 12. A series of Sr5-xBax(PO4)3OH samples had beenobtained by adding sodium hydroxide aqueous solution into the Sr-Ba-P solution to pH12.5 and following aging at 60 °C for 24h. The so-prepared samples are metallic cation-deficient hydroxyapatite solid solutions. The samples present low degree of crystallinity, irregular short rod-like morphology and nanometer size. The crystal cell parameters of Ca5-xSrx(PO4)3OH samples are nearly linear to their barium content, and their infrared absorption bands of PO43- groups shift to lower wave numbers with the increase of the barium content.

Effects of N and F doping on structure and photocatalytic properties of anatase TiO2 nanoparticles

A facile solvothermal method has been developed for preparing anatase TiO2 nanoparticles doped with nitrogen (N) or co-doped with N and fluorine (F). The effects of N and F doping or co-doping on the structural and photocatalytic properties of anatase TiO2 nanoparticles were investigated. X-ray diffraction, transmission electron microscopy (TEM), high-resolution TEM, X-ray photoelectron spectroscopy, and Raman spectroscopy were used to characterize the synthesized nanoparticles, confirming the successful synthesis of anatase TiO2. The crystal cell parameters and crystal size decreased with the doping of N or codoping of N and F. Photocatalytic degradation of methyl orange under both UV and visible light irradiation revealed that the photocatalytic activity of anatase TiO2 was greatly improved by N doping or N and F co-doping. The effect of TiO2 bandgap narrowing and the synergistic effect between co-dopants N and F on photocatalytic performance of TiO2 were also discussed. The N–F-co-doped TiO2 is thus a promising material for photocatalytic applications.

Synthesis, Phase and Structural Analysis of Compounds in the System Gd2-xNdxZr2O7 (0.0 ≤ x ≤ 2.0)

A series of compounds with the general formula Gd2-xNdxZr2O7 (0.0 ≤ x ≤ 2.0) was synthesized by high- temperature solid state method and characterized by powder X-ray diffraction. Trivalent neodymium was used as the surrogate for americium with three valences, an actinide found in radioactive nuclear wastes. The X-ray diffraction patterns show that the whole system of Gd2-xNdxZr2O7 (0.0 ≤ x ≤ 2.0) consistently possesses the pyrochlore structure. In order to get the accurate data of structural changes of zirconate pyrochlores incorporating Am3+, the Rietveld structural refinement method was employed to calculate the crystal cell parameters of zirconate pyrochlores. The calculated results indicated that the value of x in the system Gd2-xNdxZr2O7 (0.0 ≤ x ≤ 2.0) and the crystal cell parameter a accord with a = 10.52696 + 0.07036 x, x and the volume of crystal cell V follow the relation of V = 1166.45459 + 23.72163 x.

Very Intense Polarized (VIP) Neutron Diffractometer at the ORPHEE Reactor in Saclay

Abstract A new polarized neutron diffractometer has been commissioned at the ORPHEE reactor in Saclay. Hot neutron beam of 0.8 A is obtained by Heussler monochromator. 64 position sensitive detectors cover angular range of 25°×80° in vertical and horizontal directions, which allows performing measurements of flipping ratios for dozens of reflections simultaneously. Data acquisition and data treatment programs have been developed. Possibilities of multi-crystal experiments and studies of powder samples have been tested. Ensemble of these measures should boost the data acquisition rate of magnetization densities by a factor of 5-20 depending on the crystal cell parameters.

Synthesis and study of a new kind of lead complex with variable coordination numbers

The crystal C18H12O10Pb3 is synthesized by Pb and phenyl propylene acid. The crystal is characterized by IR and single-crystal X-ray diffraction. The crystal belongs to monoclinic system, space group P21/c with the crystal cell parameters of a = 15.3263(14) A, b = 16.3479(14) A, c = 8.1006(7) A, β = 92.3060(10)°, V = 2028.0(3) A3, and Z = 4. Through the molecular structure of complex, we can see that Pb has three kinds of coordination modes (5, 6, 7). The compound has formed a 1D surface shape structure through these coordinate modes with the ligand, and this 2D layer piles through C-H…π forms the 3D compound.