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Ettlingen, Germany

Mikhalychev A.,Belarusian State University | Mikhalychev A.,B. I. Stepanov Institute of Physics | Benediktovitch A.,Belarusian State University | Ulyanenkova T.,Rigaku Europe SE | Ulyanenkov A.,Atomicus GmbH
Journal of Applied Crystallography

Modeling of the X-ray diffractometer instrumental function for a given optics configuration is important both for planning experiments and for the analysis of measured data. A fast and universal method for instrumental function simulation, suitable for fully automated computer realization and describing both coplanar and noncoplanar measurement geometries for any combination of X-ray optical elements, is proposed. The method can be identified as semi-analytical backward ray tracing and is based on the calculation of a detected signal as an integral of X-ray intensities for all the rays reaching the detector. The high speed of calculation is provided by the expressions for analytical integration over the spatial coordinates that describe the detection point. Consideration of the three-dimensional propagation of rays without restriction to the diffraction plane provides the applicability of the method for noncoplanar geometry and the accuracy for characterization of the signal from a two-dimensional detector. The correctness of the simulation algorithm is checked in the following two ways: by verifying the consistency of the calculated data with the patterns expected for certain simple limiting cases and by comparing measured reciprocal-space maps with the corresponding maps simulated by the proposed method for the same diffractometer configurations. Both kinds of tests demonstrate the agreement of the simulated instrumental function shape with the measured data. Source

Zhylik A.,Belarusian State University | Benediktovitch A.,Belarusian State University | Feranchuk I.,Belarusian State University | Inaba K.,Rigaku Corporation | And 2 more authors.
Journal of Applied Crystallography

A general theoretical approach to the description of epitaxial layers with essentially different cell parameters and in-plane relaxation anisotropy has been developed. A covariant description of relaxation in such structures has been introduced. An iteration method for evaluation of these parameters on the basis of the diffraction data set has been worked out together with error analysis and reliability checking. The validity of the presented theoretical approaches has been proved with a-ZnO on r-sapphire samples grown in the temperature range from 573 K up to 1073 K. A covariant description of relaxation anisotropy for these samples has been estimated with data measured for different directions of the diffraction plane relative to the sample surface. © 2013 International Union of Crystallography Printed in Singapore - all rights reserved. Source

Feranchuk I.,Belarusian State University | Ivanov A.,Belarusan National Technical University | Ulyanenkov A.,Rigaku Europe SE
Nonlinear Phenomena in Complex Systems

Nonperturbative method for description of quantum systems - the operator method (OM) and the conception of the uniformly suitable estimation (USE) are considered for the series of real physical systems. It is shown that the OM zeroth-order approximation permits one to find the analytical approximation for eigenfunctions and eigenvalues with high accuracy within the entire range of the Hamiltonian parameters and any quantum numbers. The OM subsequent approximations converge rapidly to the exact solutions of the Schrödinger equation. The generalization of OM for the quantum statistics is also developed. Source

Vlasenko S.,Belarusian State University | Benediktovitch A.,Belarusian State University | Ulyanenkova T.,Rigaku Europe SE | Uglov V.,Belarusian State University | And 4 more authors.
Journal of Nuclear Materials

The microstructural parameters of oxide dispersion strengthened (ODS) steels from measured diffraction profiles were evaluated using an approach where the complex oxide nanoparticles (Y2Ti2O7 and Y4Al2O9) are modeled as spherical inclusions in the steel matrix with coherent or incoherent boundaries. The proposed method enables processing of diffraction data from materials containing spherical inclusions in addition to straight dislocations, and taking into account broadening due to crystallite size and instrumental effects. The parameters of crystallite size distribution modeled by a lognormal distribution function (the parameters m and σ), the strain anisotropy parameter q, the dislocation density ρ, the dislocation arrangement parameter M, the density of oxide nanoparticles ρnp and the nanoparticle radius r0 were determined for the ODS steel samples. The results obtained are in good agreement with the results of transmission electron microscopy (TEM). © 2015 Elsevier B.V. All rights reserved. Source

Benediktovitch A.,Belarusian State University | Ulyanenkova T.,Rigaku Europe SE | Ulyanenkov A.,Rigaku Europe SE
Journal of Applied Crystallography

A noncoplanar measurement geometry, achieved by using a diffractometer equipped with a detector arm possessing two degrees of freedom, is a promising technique for the analysis of residual stress gradients in polycrystalline objects and for anisotropic microstructure investigations. The instrumental function for a parallel beam and a set of two orthogonal receiving Soller slits is considered in detail, and the explicit analytical expressions in terms of a convolution of functions are derived. A comparison of the calculated results with the measured profiles from a NIST SRM 660b LaB6 powder standard sample shows a good alphaeement. © 2014 International Union of Crystallography. Source

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