In this paper, the possibility of applying graph neural networks (NN) to study the structure of copper centers of zeolites is considered. The dataset used for NN training was prepared using the FDMNES software based on the finite difference method and included more than 2100 Cu K-XANES spectra for Cu-MOR. The performed study demonstrated the capability of graph neural networks to reproduce the Cu K-XANES spectrum corresponding to a particular model of the copper center in the zeolite framework.
Keywords: zeolite, mordenite, atomic structure, XANES, machine learning, graph neural networks
Plasmonic nanoparticles make it possible to localize the electromagnetic field at scales smaller than the optical wavelength. This property is useful for the application of same objects for the creation of nanodetectors, in the processes of energy conversion and storage, in the tasks of data processing and transmission. In particular, the creation of computer chips with plasmonic elements instead of traditional semiconductors will increase their performance and energy efficiency. Our main purpose is obtaining implanted in the matrix of glass the arrays of plasmonic nanoparticles with controlled optical properties. Their properties can be varied by changing the conditions of their synthesis and post-processing. Nanoparticles are created by UV-laser influence on the gold film, precipitated on the glass surface. One of the proposed methods is long-term heating at 300 ̊C of already synthesized samples. This research presents the results of the study of the effect of temperature treatment on the atomic structure of Au nanoparticles. The study of the nanoparticles atomic structure was performed by using EXAFS-spectroscopy at the Au L3-edge. EXAFS-functions were fitted by using Stepwise EXAFS fitting-code, obtained models of the NPs atomic structure were confirmed by using DFT-optimization. The fact, that the atomic structure of NPs before and afted thermal treatment is strongly dependent of the thickness of initial gold layer (6, 10 and 70nm), is established. These differencies can be explainde by different interaction between gold film & NPs and glass matryx.
Keywords: nanoparticles, Au, nanoplasmonics, EXAFS, DFT, atomic structure
Today, catalysts based on zeolites containing transition metal ions are being intensively developed, ensuring the selectivity of the reaction of direct oxidation of methane to methanol. In current work, the X-ray absorption spectroscopy complimented with the structural models obtained in frames of the density functional theory were used to study the dependence of the local atomic structure of copper centers in mordenite type zeolites synthesized by solid-phase ion exchange using CuCl and H-MOR, upon the annealing temperature at different stages of synthesis. The typical Cu – O interatomic distances and the corresponding coordination numbers are determined. The dependence of the fraction of copper ions on the zeolite on the annealing temperature was established.
Keywords: EXAFS, DFT, zeolites, solid-phase synthesis, methanol synthesis
The structure of synthesized ferroelectric samples of PbSc0.5Ta0.5O3 after mechanoactivation were studied by means of X-ray absorption spectroscopy(XANES), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Based on the combination of effective experimental methods and computer modeling of theoretical X-ray absorption spectra near the L3 - edge of tantalum and lead was studied character of structural distortions for investigated samples after mechanoactivation.
Keywords: Ferroelectrics materials, mechanoactivation, XANES, defects
In this paper we study of the local atomic and electronic structure of nanostructured condensed material for rechargeable current sources on the basis of 15mas.%V2O5/Fe/LiF nanocomposite within charge-discharge cycle. Principle component analysis (PCA) of the series of Fe K-edge spectra collected during 1 st charge showing the concentrations of the components Fe, FeF2 and V[FeV]O4. We found the changes in the V oxidation state from the analysis of the experimental Fe K- and V K- XANES spectra. Total and partial density of states of components are presented.
Keywords: nanostructured materials for rechargeable current sources, dynamics of local atomic and electronic structures, XANES, DFT
In this paper we study the dynamics of the local atomic structure of new nanostructured condensed material for for rechargeable current sources on the basis of 15mas.%V2O5/Fe/LiF nanocomposite within charge-discharge cycle on the basis of X-ray diffraction (XRD), X-ray absorption spectroscopy (XANES) and of computer simulation. The analysis of the experimental data obtained during the first charge cycle reveals the transformation of iron to more than 50% of iron fluoride (II) , Li ions intercalate into the structure of amorphous V2O5 forming LiVO2 compound.
Keywords: diversification of management, production diversification, financial and economic purposes of a diversification, technological purposes of ensuring flexibility of production