Journal: Acta Crystallographica Section B: Structural Science Crystal Engineering and Materials

Abbreviation

Acta crystallogr., B Struct. sci. cryst. eng. mater.

Publisher

Wiley-Blackwell

Journal Volumes

ISSN

2052-5192
2052-5206

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2014 - 201922020 - 20253
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Publications 1 - 5 of 5
  • Attractive and repulsive forces in a crystal of [Rb(18-crown-6)][SbCl₆] under high pressure
    Item type: Journal Article
    Rusanov, Eduard; Wörle, Michael D.; Kovalenko, Maksym V.; et al. (2024)
    Acta Crystallographica Section B: Structural Science Crystal Engineering and Materials
    The compression behavior of [Rb(18-crown-6)][SbCl₆] crystal under pressure up to 2.16 (3) GPa was investigated in a diamond anvil cell (DAC) using a mixture of pentane–isopentane (1:4) as the pressure-transmitting fluid. The compound crystallizes in trigonal space group R3 and no phase transition was observed in the indicated pressure range. The low value of pressure bulk modulus [9.1 (5) GPa] found in this crystal is a characteristic of soft materials with predominant dispersive and electrostatic interaction forces. The nonlinear relationship between unit-cell parameters under high pressure is attributed to the influence of reduced intermolecular H. . .Cl contacts under pressure over 0.73 GPa. It also explains the high compression efficiency of [Rb(18-crown-6)] [SbCl₆] crystals at relatively low pressures, resulting in a significant shift of the Rb atom to the center of the crown ether cavity. At pressures above 0.9 GPa, steric repulsion forces begin to play a remarkable role, since an increasing number of interatomic H⋯Cl and H⋯H contacts become shorter than the sum of their van der Waals (vdW) radii. Below 0.9 GPa, both unit-cell parameter dependences (P–a and P–c) exhibit hysteresis upon pressure release, demonstrating their influence on the disordered model of Rb atoms. The void reduction under pressure also demonstrates two linear sections with the inflection point at 0.9 GPa. Compression of the crystal is accompanied by a significant decrease in the volume of the voids, leading to the rapid approach of Rb atoms to the center of the crown ether cavity. For the Rb atom to penetrate into the center of the crown ether cavity in [Rb(18-crown-6)][SbCl₆], it is necessary to apply a pressure of about 2.5 GPa to disrupt the balance of atomic forces in the crystal. This sample serves as a compression model demonstrating the influence of both attractive and repulsive forces on the change in unit-cell parameters under pressure.
  • Metastable disordered phase in flash-frozen Prussian Blue analogues
    Item type: Journal Article
    Kholina, Yevheniia; Dössegger, Janine; Weber, Mads C.; et al. (2022)
    Acta Crystallographica Section B: Structural Science Crystal Engineering and Materials
    A new metastable phase in flash-frozen disordered Prussian blue analogues is reported. The phase is characterised by the appearance of diffuse scattering clouds and the reduction of the local structure symmetry: from cubic to a tetragonal or lower space group. The phase transition is characterised by the translational modulation of the structure and is likely caused by the freezing of the water confined in the pores of the structure.
  • The quasiperiodic average structure of highly disordered decagonal Zn-Mg-Dy and its temperature dependence
    Item type: Journal Article
    Ors, Taylan; Takakura, Hiroyuki; Abe, Eiji; et al. (2014)
    Acta Crystallographica Section B: Structural Science Crystal Engineering and Materials
  • Structural and magnetic properties of β-Li$_2$IrO$_3$ after grazing-angle focused ion beam thinning
    Item type: Journal Article
    Hua, Nelson; Breitner, Franziska; Jesche, Anton; et al. (2025)
    Acta Crystallographica Section B: Structural Science Crystal Engineering and Materials
    Manipulating the size and orientation of quantum materials is often used to tune emergent phenomena, but precise control of these parameters is also necessary from an experimental point of view. Various synthesis techniques already exist, such as epitaxial thin film growth and chemical etching, that are capable of producing specific sample dimensions with high precision. However, certain materials exist as single crystals that are often difficult to manipulate, thereby limiting their studies to a certain subset of experimental techniques. One particular class of these materials includes lithium and sodium iridates, which are promising candidates for hosting a Kitaev quantum spin liquid state. Here a controlled method of using a focused ion beam at grazing incidence to reduce the size of a β-Li$_2$IrO$_3$ single crystal to a thickness of 1-2 μm is presented. Subsequent X-ray diffraction measurements show the lattice remains intact, albeit with a larger mosaic spread. The integrity of the magnetic order is also preserved as the temperature dependent magnetic diffraction peak follows the same trend as its bulk counterpart with a transition temperature at T$_N$ = 37.5 K. Our study demonstrates a technique that opens up the possibility of nonequilibrium experiments where submicron thin samples are often essential.
  • Hydrogen-substituted β-tricalcium phosphate synthesized in organic media
    Item type: Journal Article
    Stähli, Christoph; Thüring, Jürg; Galea, Laëtitia; et al. (2016)
    Acta Crystallographica Section B: Structural Science Crystal Engineering and Materials
    β-Tricalcium phosphate (β-TCP) platelets synthesized in ethylene glycol offer interesting geometries for nano-structured composite bone substitutes but were never crystallographically analyzed. In this study, powder X-ray diffraction and Rietveld refinement revealed a discrepancy between the platelet structure and the known β-TCP crystal model. In contrast, a model featuring partial H for Ca substitution and the inversion of P1O4 tetrahedra, adopted from the whitlockite structure, allowed for a refinement with minimal misfits and was corroborated by HPO42− absorptions in Fourier-transform IR spectra. The Ca/P ratio converged to 1.443 ± 0.003 (n = 36), independently of synthesis conditions. As a quantitative verification, the platelets were thermally decomposed into hydrogen-free β-TCP and β-calcium pyrophosphate which resulted in a global Ca/P ratio in close agreement with the initial β-TCP Ca/P ratio (ΔCa/P = 0.003) and with the chemical composition measured by inductively coupled plasma (ΔCa/P = 0.003). These findings thus describe for the first time a hydrogen-substituted β-TCP structure, i.e. a Mg-free whitlockite, represented by the formula Ca21 − x(HPO4)2x(PO4)14 − 2x, where x = 0.80 ± 0.04, and may have implications for resorption properties of bone regenerative materials.
Publications 1 - 5 of 5