搜索结果：Acta crystallographica Section B, Structural science, crystal engineering and materials

Although there have been several studies on the powder form, there has yet to be a report on the bulk crystal growth and its property studies of LiNiO2. In the present study, we report the first successful growth of a LiNiO2 single crystal by employing the optical floating-zone technique. Structural properties have been studied using single-crystal X-ray diffraction (XRD). The structural refinement of the single-crystal XRD data, along with the Laue diffraction patterns, confirms that this system crystallizes in a rhombohedral unit cell in space group R3m and the presence of a single grain along the length of the grown crystal. Furthermore, for the first time, we have observed and determined their superstructures as a function of temperature using single-crystal XRD. We have also conducted a study using the high flux of synchrotron X-rays to demonstrate the mechanism which drives the superstructure witnessed by the single-crystal XRD. Resonant elastic X-ray scattering was used to confirm the superstructure and the mixed valence state of different Ni sites. No additional ordering phenomena were observed, including magnetic or electronic ordering. Our study demonstrates the optimization of LiNiO2 growth parameters and provides information about atomic and electronic ordering in the system, including the onset of a superstructure phase. This will provide a basis for further work in developing improved cathode materials and understanding quantum spin liquids.

CRYSP has been developed as a crystallographic tool for the construction and visualization of crystal shapes. The input parameters for software are crystal structure files, Miller indices, and corresponding minimum surface energies. A graphical user-friendly interface is provided, along with automatic conversion from crystallographic space groups to point groups, simplifying the input of interfacial energies and their orientations. The algorithm of Wulff construction, as described in a research paper on the SOWOS software, has been modified to include a cleavage option, enabling the identification of very small facets, short edges, and nearly coincidence vertices. This enhancement allows the construction of crystal shapes both in natural habits and on planar substrates, the latter corresponding to the Winterbottom construction. Visualization in pseudo-color is provided, including facet indices and quantitative parameters such as edge length, facet area, and crystal volume. The software also supports morphologies associated with non-crystallographic point groups, e.g. icosahedral symmetry. CRYSP serves as a versatile tool for crystallography, nanostructures and any other field where crystal facets are involved.

We report a systematic study of the structural and magnetic evolution in CeAlSi1-xGex, a series of materials which provide a tunable platform for exploring magnetism in noncentrosymmetric Ce-based intermetallics. Polycrystalline samples and single crystals were synthesized using arc melting and flux growth techniques. Structural characterization by X-ray diffraction shows a continuous increase in the unit-cell parameters with increasing Ge content, with no evidence of a structural phase transition across the series. Magnetization measurements reveal a suppression of the ferromagnetic ordering temperature of CeAlSi with increasing Ge substitution, indicating a crossover toward antiferromagnetic behaviour in Ge-rich compositions. Neutron diffraction measurements performed on selected compositions show that weak magnetic intensity appears on some structural Bragg peaks below the magnetic ordering temperature. These results elucidate the relationship between chemical substitution, crystal structure, and magnetic ground states in CeAlSi1-xGex, and establish this system as a model platform for studying compositionally tuned magnetic order in noncentrosymmetric materials.

The nature of the phenomenon of negative thermal expansion was studied at the atomic level using the in-situ single-crystal and powder high-temperature X-ray diffraction (HTXRD) of Ho,Tm-doped Yb2Mo3O12 crystals grown by the flux-melt technique. Phase transitions, structure deformation and luminescence were investigated in the temperature range 303-1273 K in air. Under ambient conditions, Ho,Tm-codoped Yb2Mo3O12 has monoclinic crystal structure of Al2W3O12 (P21/c) structure type: a = 16.554 (2), b = 9.859 (1), c = 16.667 (2) Å, β = 107.88 (1)°, V = 2588.6 (5) Å3. A reversible transformation monoclinic ↔ orthorhombic occurs at about 320 K according to the HTXRD data. The orthorhombic structure [Pbcn, a = 13.7388 (2), b = 9.8582 (2), c = 9.9472 (2), V = 1347.25 (4) Å3 at 373 K] shows remarkable negative volumetric thermal expansion up to about 1173 K (average αv = -15 × 10-6 K-1); above this temperature molybdate starts to evaporate. Monoclinic modification in contrast to the orthorhombic one expands only positively. Careful analysis of the orthorhombic crystal structure from non-ambient single-crystal diffraction data showed that the bond lengths in MoO4 and YbO6 polyhedra do not change with temperature; the decrease of structure volume is due to the angular deformation of the framework built from MoO4 and YbO6 polyhedra. This study demonstrates the potential of Yb3+, Ho3+, Tm3+-codoped crystalline systems for developing a highly sensitive ratiometric optical thermometer by exploiting efficient energy transfer, a negative thermal expansion-induced emission stabilization at ∼655 nm within 570 to 800 K, and phonon-activated population of the Tm3+3F3 level for ∼700 nm emission under 980 nm excitation.

A computerized analysis of over 450 mica crystal structures is carried out. These data are accessed via the Inorganic Crystal Structure Database (ICSD), whereby unit-cell parameters, atomic coordinates and polyhedron generators resulting from this analysis are transferred to Microsoft Excel as an interactive working environment. This environment enables the rapid calculation of many crystal chemical parameters, including tetrahedral, octahedral or AO12 polyhedral volumes and areas. The forms of the O4 tetrahedra are quantified by transformation to pseudocubes with six independent parameters. Reversibility between crystal chemical and crystallographic parameters is provided by means of the Microsoft Excel Solver. This gives rise to a method of structure prediction by interpolation, which is demonstrated for a 1M phlogopite. Hypothetical structures at temperatures of 150 and 723 K are predicted, and a computationally generated structure at 673 K is compared with the experimentally known structure at this temperature. The crystal chemical parameterization is also used to identify the differences between the five principal mica polytypes: 1M, 2M1, 2M2, 3T and 2O. The Excel software developed is made available via a weblink, with instructions for carrying out structure predictions in the supporting information.

Polymers have been widely used to physically stabilize amorphous drugs by forming amorphous solid dispersions (ASDs), resulting in commercial and clinical success as a pharmaceutical technique to improve the bioavailability of a poorly water-soluble drug. However, the role of polymers in maintaining the physical stability of ASDs has not been fully understood. Herein, we investigated how poly(methyl methacrylates) (PMMAs) with different tacticities impact the liquid dynamics and crystallization kinetics of amorphous griseofulvin (GSF). PMMAs with similar chain lengths and identical monomer structures were selected, aiming to exclude effects arising from differences in monomer structure and end groups. The syndiotactic form of PMMA (s-PMMA) exhibited a stronger inhibitory effect on the crystal growth of amorphous GSF in comparison with isotactic (i-PMMA) and atactic (a-PMMA) forms. Effects of the isotactic atactic forms of PMMA on the crystal growth of GSF can be mainly attributed to their molecular mobility, as shown by the overlapping of the logarithm growth rate curves versus viscosity and α-relaxation time. However, the crystal growth rate curves of GSF in the system containing 10 wt% s-PMMA did not overlap with those of the pure GSF system. These results suggest that liquid dynamics is not a main contributor to the inhibitory effect of s-PMMA during drug crystallization.

A series of 12 compounds: Na(H3P2O6) (1 and 2), Na(H3P2O6)·H2O (3), Na2(H2P2O6) (4 and 5), Na2(H2P2O6)·2H2O (6), Na2(H2P2O6)·6H2O (7 and 8), Na5(H2P2O6)(HP2O6)·21H2O (9), Na3(HP2O6) (10 and 11) and Na3(HP2O6)·9H2O (12) has been characterized by variable-temperature optical microscopy, thermogravimetry, single-crystal and powder X-ray diffraction. Crystalline salts 1-4, 6-10 and 12 have been obtained in typical solution crystallization processes. Dehydrations of Na(H3P2O6)·H2O (3), Na2(H2P2O6)·6H2O (both 7 and 8) and Na3(HP2O6)·9H2O (12) were monitored by TGA, variable-temperature microscopy and powder or microsample powder X-ray diffraction, and turned out to be one-step, destructive transformations, resulting in almost pure triclinic form of Na(H3P2O6) (1), α-Na2(H2P2O6) (4) and α-Na3(HP2O6) (10), respectively. Sodium ionic conductivity was calculated using the bond valence sum method for all obtained anhydrous substances and measured for the best candidate, compound 4 in the temperature range 300-420 K, reaching 10-4 S m-1.

The response of the 1,5-tolyl-3-phenyl-6-oxo-verdazyl radical (pTolOV) to pressure in the crystalline state has been investigated using both high-pressure X-ray diffraction techniques and density functional theory (DFT) calculations. Changes in structure, electronic properties such as band gap and density of states, and magnetic exchange interactions have been explored. Structural analysis reveals a phase transition between the P21/n and C2/c space groups between 2.30 and 2.73 GPa, and an accompanying increase in molecular point group symmetry in the solid state structure at higher pressures. Modelling using periodic DFT-based methods reveals no significant energy penalty to this phase transition with a small reduction in the band gap upon increasing pressure due to changes in the intermolecular distances, before a sharp increase in band gap with the changes in intermolecular alignment in the C2/c phase. These variations fall in the range 2.02-1.94 eV, and the radical remains a wide-gap semiconductor in the solid state across the pressure range examined. Further DFT calculations with gas-phase models reveal weak antiferromagnetic exchange interactions occurring in antiparallel π-stacked chains in both phases.

Experimental results of growth of (Cr, Co, Fe)-co-doped ZnSe crystals, for laser applications in the range 2-5 µm, by the vertical Bridgman method under high argon pressure are described for the first time. A comparative study involving crystallographic analysis, X-ray diffraction, scanning electron microscopy, infrared spectroscopy, and other physical characterization techniques is carried out for co-doped (Cr, Co, Fe):ZnSe crystals. Growth features, morphology and optical properties of the crystals are studied and correlated with their crystal structure. The feasibility of producing large, homogeneous optical crystals with a controlled and uniform distribution of multiple activators throughout the crystal volume is also demonstrated.

Three novel Schiff base ligands were synthesized through the condensation reaction of 2-(methylamino) or 2-(ethylamino)benzaldehyde with ethylenediamine and 4-nitro-1,2-phenylenediamine, respectively. The resulting Schiff bases were thoroughly characterized using FTIR, 1H NMR and UV-vis spectroscopies, and their crystal structures were elucidated through single-crystal X-ray diffraction. Additionally, computational methods based on noncovalent interaction index and quantum theory of atoms in molecules were employed to investigate the intra- and intermolecular interactions in the molecular structure and crystal packing. The origin of the electronic transitions in UV-vis spectra of the Schiff base ligands were also investigated using time-dependent density functional theory along with the electron density difference map. Furthermore, energy decomposition analysis combined with natural orbitals for chemical valence theory has been performed to estimate the pairwise interaction energies in the dimer associates aggregated by the intermolecular interactions in the Schiff base ligands.

Artemisinin (ART) is mainly used for the treatment of malaria and exhibits polymorphism with two known crystalline forms. In this study, the high-pressure behaviour of these two polymorphs was investigated to evaluate their compressibility and identify if any pressure-induced phase transitions occur with a view to assessing the impact of manufacturing pressure on the active pharmaceutical ingredient. Form (I), the orthorhombic polymorph, is found to be the most compressible of the three. Form (II), a triclinic phase, undergoes a phase transition to a new polymorph that is observed at different pressures depending on the pressure-transmitting medium (PTM) used. The transition to form (III) occurs at 0.75 GPa when compressed in petroleum ether, however, this transition is delayed to 2.02 GPa in silicone oil. This highlights the influence of the PTM on the stability of the crystal structure. The newly characterized form (III) shares structural similarities with form (II) but differs in symmetry where a pseudo-21 screw axis in form (II) becomes a formal 21 screw axis in form (III), resulting in a change from triclinic to monoclinic and a reduction of the asymmetric unit from Z' = 4 to Z' = 2. These findings contribute to a deeper understanding of pressure-induced polymorphism in ART and underscores the importance of external factors such as PTM in influencing solid-state transitions relevant to pharmaceutical processing and formulation.

Charge density and local electrostatic and quantum kinetic electron forces acting on the bound atoms in [Co(NH3)5NO2]ClNO3 (nitro isomer) and [Co(NH3)5ONO]ClNO3 (nitrito isomer) were studied to elucidate to the role of the crystalline environment in the intramolecular nitro-nitrito linkage photoisomerization. Quantum crystallography and orbital-free DFT approaches were applied. In the more stable nitro isomer, the -NO2- group forms two hydrogen bonds with the NH3 ligands, while in the nitrito isomer the -ONO- group is not involved in any hydrogen bonds, however, it forms van der Waals contacts with surrounding atoms. No bond paths in the electron density were found between the anions NO3- and Cl-, which were previously supposed to play an important role in photoisomerization. Still, these anions do interact with each other in both isomers via an indirect mechanism involving H atoms of -NH3 ligands. Whereas there is no direct electrostatic interaction between the anions in the nitro isomer, the part of electrons belonging to the Cl- anion in the nitrito isomer is pulled towards the nucleus of an oxygen atom of the NO3- anion, creating a favorable condition for direct interaction between anions through corresponding local electronic forces directed to the nuclei. The link of cation/anion atomic basin volumes relationship and nature of the intermolecular interactions is established.

An emerging cubic substrate material (Nd,Sr)(Al,Ta)O3 (NSAT) has been analysed using powder and single-crystal X-ray diffraction, transmission electron microscopy, infrared (IR) and ultraviolet-visible range ellipsometry as well as IR- and Raman spectroscopies. Based on this experimental characterization, the structure and vibrational properties are described with improved understanding. On a large length scale the NSAT substrate is found to have a basic simple cubic perovskite structure (a = 3.8427 Å) that, on a small length scale, is subdivided into superstructure ordered nanoscale domains with doubled lattice (unit-cell) parameter (a = 7.6855 Å). Ellipsometry and vibrational spectroscopy show absorption bands consistent with the expected structure type, however, the peak widths indicate significant local deviations from the perfectly ordered superstructure or ideal solid solution. Since the lattice parameter is unaffected, the observed inhomogeneity is not expected to affect the use of NSAT as a substrate for most applications.

Single-crystal X-ray diffraction is one of the most reliable techniques for elucidating the molecular structures, while it requires high-quality single crystals. The crystalline mate (CM) strategy has recently emerged as an effective method to induce rapid and selective co-crystallization. Here, we demonstrate that this strategy can be reliably extended to ionic systems using the neutral trinuclear silver pyrazolate complex Ag3Pz3 as a crystallization mate. By regulating solvent polarity, two co-crystals of silver pyrazolate berberine hydrochloride Ag3Pz3·BCl, SF (sandwich form) and NSF (non-sandwiched form), were obtained. In SF, neutral Ag3Pz3 simultaneously engages the Cl- anion via π-acid/base contacts and the berberine cation through weak Ag...O coordination. Remarkably, SF can also be crystallized directly from crude Coptis chinensis extract without prior purification. In NSF, due to the influence from methanol or ethanol, Ag3Pz3 rearranges into a rare anionic Ag3Pz4 cluster that serves as the counterion to berberine. These results establish solvent polarity as a decisive factor governing CM-mediated co-crystal assembly and broaden the applicability of the crystalline-mate concept to ionic systems.

tert-Butylcalix[6]arene (TBC6) exhibits a rich crystal energy landscape, with structural diversity driven by macrocycle conformation, guest inclusion and self-assembly. Using multicomponent crystallization mixtures containing DMSO and additional solvents (e.g. DMF, chlorobenzene, 1,2-dichlorobenzene, anisole, THF), we obtained seven new TBC6 solvates. One structure, crystallized in the presence of pyridine, adopts a winged-cone conformation with a bilayer arrangement in the crystal. The remaining six are isostructural and feature a columnar packing of TBC6 in a 1,2,3-alternate conformation stabilized by four strong interactions with DMSO: two hydrogen bonds and two C-H...π interactions. Notably, DMSO in the TBC6 cavity is released at elevated temperatures (∼200°C), consistent with its stronger binding energy as calculated using DFT methods. TBC6-TBC6 interactions, both within and between columns, dominate the crystal packing, with intracolumnar contacts contributing twice as much stabilization as intercolumnar ones, where additional solvent guests are located. Hirshfeld surface analysis supports these findings, highlighting extensive contact areas between TBC6 molecules. This study contributes to understanding how solvent properties, interaction energies, and packing preferences drive the solid-state organization of calixarenes-molecules with broad applications in separation, recognition, and supramolecular chemistry.

Single crystals of lacunary apatite structure-type compound Pb4Na(PO4)3 were prepared with a flux/solid-state-reaction technique and consecutive melt-growth to examine spatial distribution and stereochemical activity of the 6s2 lone electron pair of Pb2+ using X-ray diffraction. The target compound crystallized in space group P63/m with unit-cell edge lengths a = 9.7345 (12) Å and c = 7.2130 (18) Å without any indication of configurational ordering of Pb2+ and Na+ at the crystallographic A1 site. The anion channel running through the structure was confirmed as vacant. Residual density attributable to the deformed 6s2 electron cloud was found 0.6 Å apart from the A2-site position on the A2 triangle normal to c. The lack of a channel-site anion induced shrinkage of the unit cell and the O3 trigonal antiprism in the xy plane, and an increase in the twist angle of the A1O6 trigonal metaprism compensated for the shrinkage of the latter to keep the volume of the A1O9 coordination polyhedron constant. Systematic comparison of the size of the A2 triangle in Pb4Na(PO4)3 and other apatite-type compounds indicates no contribution from the 6s2 electron orbital on the size of the A2 triangle and limited space-filling ability of the orbital. A2 cations are attached on the periphery of a large void formed by the in-plane distortion of the hexagonal close packed arrangement of (BO4)3- complex anions. In other words, a face-sharing array of A2 octahedra was inserted `as a tube' through the framework. The sizes of A1O9 and BO4 polyhedra and their framework define the maximum size of the A2 triangle, while the triangle can easily be shrunk by attraction from an anion, such as F-, in the channel.

Single crystal specimens of Fe2.992O4 (magnetite), Fe3-x-yMnx□yO4 (x ≤ 0.980) and Fe3-x-yNix□yO4 (x ≤ 0.513, □ denotes point defects) are prepared using a floating-zone technique, and changes in their structural parameter values with x are examined at room temperature. Preferences of Mn, Ni and point defects at A, B and B sites, respectively, are confirmed by single-crystal X-ray diffraction experiments, while preference of Mn at the A site is not perfectly accomplished in Fe2.010Mn0.980O4. Mean-square displacements of atoms along the 3 axis in [111] are peculiarly large at the B site in Fe2.992O4 and the displacement decreased smoothly in both series, to nearly half in Fe2.00Mn0.980O4, with increasing amount of heteroatom. On the other hand, displacements normal to the direction show only slight convexity with x due to coexistence of the heteroatom. As a result anisotropy in displacements (dominant in [111] at x = 0) is inverted at x = 0.3 in FeMn series and would expectedly be inverted at x ≃ 0.55 in FeNi series. In spite of different locations of heteroatoms and slightly different inversion points on anisotropy, changes in mean-square displacements at the B site in [111] in these series are found on similar lines with changing amounts of heteroatom. In other words, the amount of this displacement is a function of the amount of Fe2+, or remnant electron from the itinerant-electron point-of-view, on the B-site substructure in these compounds. This characteristic lattice mode on the B-site substructure could be interpreted as an average of local distortion of the substructure due to `trimeron' [Senn et al. (2012). Nature, 481, 173-176] and some other modes such as distortion in 〈001〉 [Siratori & Kino (1980). J. Magn. Magn. Mat. 20, 87-90], which moves in the high-temperature structure.

This study presents the atomic structure solution of a primitive icosahedral Zn70.83Mg20.31Er8.86 quasicrystal using in-house X-ray diffraction and the Ammann-Kramer-Neri tiling framework. The structural model with 344 parameters refined against 2674 Bragg peaks achieves a reasonable R factor of 0.1407. Both Bergman and Tsai clusters, key motifs in the quasicrystal architecture, are identified within the structure, suggesting a hybrid character that bridges traditionally distinct quasicrystal types. The Tsai clusters show positional disorder and unusually short Mg-Mg distances (∼2.3 Å), hinting at the complex nature of the bond. Despite only moderate data resolution, the model reveals phason-related features and relatively low phasonic disorder, consistent with previously modelled Zn-Mg-Tm. This work demonstrates that the tiling can reliably reproduce real atomic configurations, which supports the use of models based on the Ammann-Kramer-Neri tiling in quasicrystalline atomic structure research. The findings contribute to ongoing efforts to decode the structural diversity and physical properties of rare-earth-containing quasicrystals.

The special issue on crystal growth and related characterization is introduced. The articles were originally published in recent regular issues of Acta Crystallographica Section B.