Journal of Applied Crystallography最新文献

Heterogeneous lyophobic systems (HLSs), i.e. systems composed of a nanoporous solid and a non-wetting liquid, have attracted much attention as promising candidates for innovative mechanical energy storage and dissipation devices. In this work, a new HLS based on a pure silica chabazite (Si-CHA) and a ternary electrolyte solution (KCl + CaCl₂) is studied from porosimetric and crystallographic points of view. The combined approach of this study has been fundamental in unravelling the properties of the system. The porosimetric experiments allowed the determination of the energetic behaviour, while high-pressure in situ crystallographic analyses helped elucidate the mechanism of intrusion. The results are compared with those obtained for systems involving the same zeolite but intruded with solutions containing only single salts (CaCl₂ or KCl). The porosimetric results of the three Si-CHA systems intruded by simple and complex electrolyte solutions (KCl 2 M, CaCl₂ 2 M and the mixture KCl 1 M + CaCl₂ 1 M) suggest that the intrusion pressure is mainly influenced by the nature of the cations. The CaCl₂ 2 M solution shows the highest intrusion pressure and KCl 2 M the lowest, whereas the mixture KCl 1 M + CaCl₂ 1 M is almost in the middle. These differences are probably related to the higher hydration enthalpy and Gibbs energy of Ca²⁺ compared with those of K⁺. It has been demonstrated that partial ion desolvation is needed to promote the penetration of the species, and a higher solvation energy requires higher pressure. The `intermediate' value of intrusion pressure shown by the complex electrolyte solution arises from the fact that, statistically, the second/third solvation cation shells can be assumed to be partially shared between K⁺ and Ca²⁺. The stronger interaction of Ca²⁺ with H₂O molecules thus also influences the desolvation of K⁺, increasing the pressure needed to activate the process compared with the pure KCl 2 M solution. This is confirmed by the structural investigation, which shows that at the beginning of intrusion only K⁺, Cl⁻ and H₂O penetrate the pores, whereas the intrusion of Ca²⁺ requires higher pressure, in agreement with the hydration enthalpies of the two cations.

Multifitting is a computer program that was originally designed to model the reflection and transmission of shortwave radiation by multilayer nanofilms. Three years have passed since the introduction of this software, and in this paper the focus is on describing the possibilities of Multifitting with regard to off-specular diffuse scattering and grazing-incidence small-angle scattering. The approach to the user interface and to working with the structure model remains the same, and the emphasis is on the ergonomics, calculation speed and intensive use of the program for technological and research tasks. However, the scope of the program has been expanded to make it more useful to existing users, and it may also be of interest to a wider audience.

Since the development of anionic group theory, the spatial arrangement of anionic groups in optical crystals has been believed to determine their functional, such as nonlinear optical, properties. At the same time, cation substitution, resulting in either the appearance of disordered cation sites in a crystal structure or the emergence of cation-ordered superstructures, has been widely used to control material properties. This work demonstrates the coupling between positional cation disorder and orientational disorder of (CO₃)²⁻ anions in the β modification of the recently described K₂Ca₃(CO₃)₄ material. In contrast to the α modification [P2₁2₁2₁, a = 7.39134 (18), b = 8.8153 (2), c = 16.4803 (4) Å], where the ordered cation sublattice favors the non-centrosymmetric orientationally ordered arrangement of (CO₃)²⁻ anionic groups, positional cation disorder in β-K₂Ca₃(CO₃)₄ [Pnma, a = 7.5371 (2), b = 16.1777 (5), c = 8.7793 (3) Å] within the cation sublattice of the same topology leads to orientational disorder of (CO₃)²⁻ groups and the appearance of an inversion center in the average structure.

This work presents present iModel, an interactive 3D crystal structure visualization program capable of reading crystal structure datafiles in various formats and rendering corresponding 3D models. Users can interact with the models by translating, rotating and zooming in on them. The software visualizes crystal structures, including atoms, bonds, unit cells and polyhedral shapes using spheres, lines and polyhedra, with customizable colors and sizes for individual atoms and bonds. The software features perspective and orthogonal projections, multiple chemical bond search modes, and a user-friendly toolbar for view control, and exports models as images or saves progress in project files. Developed on the LabVIEW platform with Python extensions, the iModel program leverages a queue message handler and producer–consumer pattern for a modular, reusable and powerful crystal structure visualization tool.