Crystallography Reports最新文献

Samples of CdTe-based crystals have been characterized. The elemental and phase compositions of the samples have been determined. The microhardness of the samples on two mutually perpendicular surfaces has been examined. It is shown that crystals with the main CdTe phase and different dopants exhibit no microhardness anisotropy. In crystals with the main CdZnTe phase, microhardness anisotropy has been found, which is related to different lengths of Cd–Te and Zn–Te bonds, which results in nonsymmetrical distortions of the crystal lattice. The observed difference in the microhardness of the CdTe crystals is explained by the difference in their structural parameters.

The structure and properties of huanzalaite MgWO₄ have been simulated by the method of empirical interatomic potentials. The structure and the elastic and thermodynamic properties of MgWO₄ have been evaluated. The results obtained are compared with the available experimental and ab initio calculation data.

Zn(_{{1-x}})Mg_xWO₄ solid solutions have been simulated by the method of empirical interatomic potentials. The dependences of the structure, elastic and thermodynamic properties on the composition have been established. It is shown that, as the magnesium fraction in the solid solution increases, the unit-cell volume, density, enthalpy, heat capacity, and entropy decrease, while the shear and bulk moduli increase. The dependences are close to linear. The mixing functions have been calculated. The enthalpy and volume of mixing are nonzero, which indicates that the solution is not ideal. It is shown that the Zn(_{{1-x}})Mg_xWO₄ solution exists over the entire range of compositions.

Intermediate states of the complex of the macrophage migration inhibitory factor (MIF) with the covalent inhibitor phenylisothiocyanate (PITC) were studied by X-ray diffraction analysis. It was demonstrated that the covalent modification of the N-terminal proline is preceded by the non-covalent binding of the inhibitor in the previously unknown holding site. The holding site was identified due to the use of short-term soaking of a MIF crystal in a ligand-containing cryo-solution followed by flash freezing in a nitrogen stream to collect the X-ray diffraction data at 100 К. A comparison of this structure with the crystal structure of the pre-modified protein revealed the details of the dynamics of the PITC binding.

The results of the first measurement of the rocking curve of a nanofocusing compound refractive lens made of silicon, used for focusing synchrotron radiation (SR) at the “KISI-Kurchatov” source, are presented. The obtained curve is accurately approximated by a Gaussian function, and its width is in agreement with the previously developed analytical theory, describing the SR propagation in multi-element focusing systems. The results demonstrate the feasibility of using the rocking curve as an alignment characteristic of the experimental setup when working with silicon lenses at second-generation SR sources.

The fluorine ion mobility in Pb_0.8M_0.2F₂ and Pb_0.75M_0.2K_0.05F_1.95 (M = Ca, Ba) solid solutions with fluorite structure under normal conditions was calculated using classical molecular dynamics. It was shown that isovalent substitution of lead atoms by calcium atoms in a lead fluoride crystal increases the mobility of fluorine ions, while a similar substitution by barium atoms decreases it. Heterovalent substitution Pb → K naturally increases the fluorine ion mobility in the Pb_0.75Ca_0.2K_0.05F_1.95 and Pb_0.75Ba_0.2K_0.05F_1.95 solid solutions.

When studying the internal structure of objects consisting of several dissimilar parts by computed tomography, there often arises a necessity of using radiations of different types, interacting with matter in different ways. Examples of such are synchrotron radiation and thermal neutrons. In this case, a method for joint analysis of data obtained under different conditions should be developed. A method for superposition of three-dimensional data arrays based on determining the coordinates of four reference points and an affine transformation of the coordinate system is proposed. Examples of combining results of studying cultural heritage objects using neutron and synchrotron tomography are presented.

The features of ion transport in lithium tetraborate Li₂B₄O₇ crystals with vacancy disorder have been studied by the molecular dynamics method. It is shown that the ion transport caused by lithium ions is anisotropic. The highest values of diffusion coefficients are observed along the c axis; they amount to D_Li ~ 1 × 10^–6 cm²/s at temperatures close to the melting point. It is shown that lithium ions jump over distances from 1.5 to 3.5 Å via the vacancy mechanism. The length of correlated jumps may reach 6 Å.

The results of studying the low-energy secondary electronic spectra of fluorine-substituted furan‒phenylene co-oligomer films in the energy range from 5 to 20 eV above E_F are reported. Thermal vacuum deposition of films with a thickness of 8–10 nm was performed on the surface of silicon substrates and layer-by-layer deposited ZnO. The energy position of the main peaks of the density of electronic states in the conduction band of the investigated films and the properties of the potential barrier between the films and substrate surfaces was determined. The surface topography of the thin films of the fluorine-substituted furan‒phenylene co-oligomer was studied by atomic force microscopy. The films on the ZnO surface have a granular structure with a grain diameter of ~100 nm in the surface plane. Grains on the (SiO₂)n-Si surface have an elongated shape, characteristic of microwhiskers.