Vol 69, No 2 (2024)

The editorial board of the journal “Crystallography” continues to publish thematic issues devoted to growth, structure, composition and properties of both inorganic and organic materials.
This issue is dedicated to the 80th anniversary of the founding of the A.V. Shubnikov Institute of Crystallography. This issue is dedicated to the 80th anniversary of the founding of the A.V. Shubnikov Institute of Crystallography of the Russian Academy of Sciences.

The emergence and development of X-ray crystallography of macromolecules or protein crystallography is one of the outstanding scientific achievements in the 20th century. The ability to determine the spatial structure of macromolecules of proteins and nucleic acids at the atomic level has ensured the rapid development of molecular biology, biochemistry, bioengineering, biotechnology, and enabled to reach the modern level of pharmacology. The review presents the results of a series of protein structure studies performed at the A. V. Shubnikov Institute of Crystallography, the Russian Academy of Sciences, starting from the 1960s and up to the present day.

Works performed at the A. V. Shubnikov Institute of Crystallography on the development of UV range optical filters based on complex compounds of nickel and cobalt are reviewed. The structural relationships of the crystal optical properties and their thermal stability are considered. Fundamental features of mixed crystals grown from solution and advanced approaches to creating optical filters based on structurally perfect mixed crystals K₂(Co, Ni)(SO₄)₂ · 6H₂O are described. The possibility of creating UV-A optical filters by partial substitution of the ligand environment of transition metal ions is demonstrated.

The dynamics of the diffraction peak 0012 parameters of LiNbO₃:Fe crystals with a time resolution of less than 1 ns were recorded by synchronizing nanosecond laser pulses with electron bunches of the KISI-Kurchatov synchrotron source. The influence of a laser pulse (λ = 532 nm, t = 4 ns, energy density 0.6 J/cm²) at different polarization directions of the laser radiation causes a change in the peak intensity, which depends on the angle between the polarization direction of the laser radiation and the crystallographic axes. The obtained results are supplemented with wavelet analysis of experimental data. The observed polarization dependence correlates with published data on the photovoltaic effect.

The morphology and crystal structure of Au nanoparticles obtained by irradiating an aqueous solution of Hydrochloroauric acid (HAuCl₄) with laser pulses were investigated using transmission electron microscopy, electron diffraction, and electron tomography methods. Along with round and shapeless particles characterized by a cubic structure with twins, there are flat particles with trigonal morphology. Such particles have a layered microstructure, with an alternation of face-centered cubic and close-packed hexagonal crystal structure of layers parallel to the base planes of the prism.

Rare-earth molybdenum-containing oxides of nominal composition Li_xNd₅ – _xMo₃O₁₆ ± _δ (x = 0, 0.05, 0.15, 0.25) with a fluorite-derived structure were first obtained as single crystals from a melt solution and by solid-phase synthesis in air as polycrystalline samples. The new phases were characterized by X-ray phase analysis, synchronous thermal analysis, and impedance spectroscopy. X-ray structural analysis showed that lithium atoms are localized near the positions of rare-earth cations. The chemical formula of the investigated single crystal was determined as Li_0.216Nd_4.784Mo₃O_14.1+δ. A small amount of lithium did not significantly affect the ability of the studied phases to undergo dissociative water absorption but led to a decrease in the total conductivity of lithium-doped Li_xNd₅ – _xMo₃O_{16 ± δ} ceramics.

The oligomeric state of the nucleoid-associated protein IHF (integration host factor) plays a significant role in organizing and compacting bacterial nucleoids, as well as in the process of bacterial resistance to adverse environmental conditions, including antibiotics. Although IHF was identified more than 25 years ago, the molecular mechanisms of its involvement in such processes remain poorly understood. In this study, using small-angle X-ray scattering, various oligomeric forms of IHF were first identified in aqueous solution depending on the presence of metal cations. It was found that the presence of Mg²⁺ and K⁺ ions inhibits the formation of high-order oligomers. The obtained data can be useful in developing strategies to overcome bacterial resistance to drugs.

New approaches in X-ray visualization of joints using various radiation sources are considered. Investigations of the structure of joint cartilage tissue and model objects structurally and functionally similar to cartilage tissue were conducted using X-ray radiation from a laboratory microtomograph and synchrotron radiation. Images of the internal structure of model objects and cartilage tissue impregnated with X-ray contrast agent were obtained using projection radiography and microtomography methods. Colloidal solutions of biocompatible nanoparticles of titanium and molybdenum oxides were used as contrasting agents. The nanoparticle concentration distribution through tissue depth was measured by image processing.

The structural and transport characteristics of the behavior of the fluorine-ion sublattice in the solid solution Pb_0.78Sr_0.19K_0.03F_1.97 were studied using the method of non-empirical molecular dynamics. It is shown that the local diffusion of fluoride ions varies depending on the nature of the dopant atom, which is consistent with experimentally observed transport characteristics.

The features of aluminum localization and the mechanism of donor center formation in ZnO:Al layers synthesized by high-frequency magnetron sputtering are studied. It is shown that aluminum predominantly localizes at grain boundaries of zinc oxide in its own oxide phase. The mechanism of aluminum oxidation at grain boundaries significantly depends on the oxygen content in the working chamber: during sputtering in an atmosphere of pure argon under conditions of oxygen deficiency, aluminum oxidation occurs as a result of interaction with oxygen from the surface layer of zinc oxide crystallites, forming surface donor centers at grain boundaries. With an increase in the partial pressure of oxygen, aluminum is predominantly oxidized by oxygen from the gas atmosphere, forming its own barrier phase at grain boundaries.

Nanoparticles of LiRF₄ (R = Y, Yb, Lu), activated with Yb³⁺/Er³⁺ and Yb³⁺/Tm³⁺ ions, were obtained by the high-temperature co-precipitation method. The influence of the precursor molar ratio and the cationic composition of matrices on their dimensionality and morphology was studied. A method for the heterogeneous crystallization of these compounds using LiYF₄ nanoseeds was optimized, which opens up opportunities for controlled synthesis of LiRF₄ nanoparticles with controllable characteristics. Among the studied objects, LiYF₄@LiYbF₄:Tm³⁺@LiYF₄ nanoparticles demonstrate the most intense anti-Stokes photoluminescence in the UV (λ = 362 nm) and blue (λ = 450 nm) ranges, exceeding similar indicators for β-NaYF₄:Yb³⁺/Tm³⁺@NaYF₄ particles. LiYF₄@LiLuF₄:Yb³⁺/Er³⁺@LiYF₄ nanoparticles are the most efficient converters of IR radiation in the λ = 1530 nm range among the investigated isostructural matrices and exhibit similar spectral-luminescent properties to the β-NaYF₄:Yb₃+/Er₃+@NaYF₄ compound with an equivalent degree of codoping. The obtained results allow considering LiYF₄@LiYbF₄:Tm³⁺@LiYF₄ and LiYF₄@LiLuF₄:Yb³⁺/Er³⁺@LiYF₄ nanoparticles as a real alternative to the most widely used phosphors based on the hexagonal matrix β-NaYF₄ for photonics and biotechnology applications.

The results of the crystallization studies of anthracene, tetracene, and pentacene under conditions of vapor phase transport in growth systems with single- and two-zone thermal fields are presented. The features of the phase behavior and thermal stability of the compounds were studied by using the methods of differential scanning calorimetry and thermogravimetric analysis to establish the heating regimes of substances ensuring crystal growth without damage from chemical degradation. Conditions for growing crystals of centimeter scale (0.2–2 cm) were determined for growth systems with single- and two-zone thermal fields. Based on the grown pentacene crystals, a series of field-effect transistors with top drain/source electrodes and top gate were fabricated and their electrical characteristics were studied.

Based on thermodynamic-topological analysis, the concentration regions for obtaining homogeneous crystals in the MF₂–M'F₂–RF₃ systems (M≠M' = Ca, Sr, Cd, Ba and Pb, R = rare earth elements, REEs) were determined. Fluorite solid solution crystals in the PbF₂–CdF₂–RF₃ systems (R = Tb, Ho, Er, Tm, Yb and Lu) were grown by the vertical directional crystallization technique. Their phase composition and distribution of components along the length of the crystalline boule were studied. Crystals of congruently melting solid solutions (Pb_0.67Cd_0.33)_1–xR_xF_2+x (R = Tb, Ho, Er, Tm, Yb, Lu) were grown for the first time. In crystals with R = Ho, Er, Tm and Yb traces of low-temperature ordering of the solid solution were found – phase isostructural to the Pb₂YF₇ compound (sp. gr. I4/m), in which the Y positions are occupied by the corresponding R cations, and the Pb positions can be partially replaced Cd cations. Crystals with R = Tb and Lu have a high degree of homogeneity and are suitable for optical research.

A brief retrospective of the development of laboratory X-ray microtomography at the A. V. Shubnikov Institute of Crystallography of the Russian Academy of Sciences (IC RAS) is presented. The main methods and approaches that have increased the informativeness of microtomographic measurements are outlined, such as the use of monochromatic radiation, the application of phase-contrast method, and the method of diffraction tomography (topo-tomography). The designs of the instruments created and operating at IC RAS are described, and some experimental results obtained with them are presented.