# A. A. Guda's research while affiliated with Rostov State Transport University and other places

## Publications (37)

Article
Micro X-ray fluorescence (XRF) analysis, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Mössbauer and X-ray absorption near-edge structure (XANES) spectroscopies have been used to study the element and phase composition, and Fe and Ni oxidation states in ordinary chondrites. The meteorit...
Article
Full-text available
X-ray absorption near-edge structure (XANES) spectra are the fingerprint of the local atomic and electronic structures around the absorbing atom. However, the quantitative analysis of these spectra is not straightforward. Even with the most recent advances in this area, for a given spectrum, it is not clear a priori which structural parameters can...
Article
Modern synchrotron radiation sources and free electron laser made X-ray absorption spectroscopy (XAS) an analytical tool for the structural analysis of materials under in situ or operando conditions. Fourier approach applied to the extended region of the XAS spectrum (EXAFS) allows the estimation of the number of structural and non-structural param...
Article
Based on machine-learning algorithms, a method is developed for determining the structural parameters of the components of a mixture from X-ray absorption spectra. For each component, a database of spectra is constructed for all possible deformations of its structure. The machine-learning method implemented in the PyFitIt software package allows qu...
Article
Surface plasmon resonance is sensitive to the size and shape of gold nanoparticles. The quantitative analysis of the ultraviolet-visible spectra provides information about the structural parameters of the nanoparticles. This task is related to the inverse design problem where machine learning (ML) algorithms show superior performance over classical...
Article
LiCoPO4 was synthesized in a short time by a microwave-assisted solvothermal technique at 220°C. The as-prepared samples are characterized as belonging to the Pn21a symmetry group, having poor electrochemical performance, and low specific capacity around 30 mAh/g. Further, activation at 700°C under air and argon increased the specific capacity to 5...
Article
Valence tautomer transition occurs mainly in 3d metalorganic complexes with redox-active ligands and makes them potential candidates for single-molecular switches. The transition occurs under temperature, pressure, or light-induced stimuli and is strongly affected by the intermolecular interactions. However single-crystal X-ray diffraction is not a...
Article
We analyzed two amorphous multilayer nanostructures (MLNS) [(CoFeB)60C40/SiO2]200 and [(CoFeB)34(SiO2)66/C]46 with the same element composition, but with the inverse location of the non-metallic phases C and SiO2 in the metal-composite layers or interlayers. Based on the analysis of XPS and X-ray absorption spectra, it was found that in the metal-c...
Article
Zn–F co-doped TiO2 nanomaterials were prepared by the sol-gel method. The effect of various amounts of modifying additives (0.1–2 mol% Zn and 0.1–4 mol% F) and calcined temperature (500–900 °C) on the properties of the obtained materials were studied. X-ray diffraction, transmission electron microscopy, scanning electron microscopy, UV–Vis spectros...
Article
Palladium-based catalysts are exploited in the industrial scale for selective hydrogenation of hydrocarbons. Formation of palladium carbide and hydride phases under reaction conditions changes the catalytic properties of the material, which points to the importance of operando characterization for determining a relation between the relative fractio...
Article
In this work we have applied machine learning methods (Extra Trees, Ridge Regression and Neural Networks) to predict structural parameters of the system based on its XANES spectrum. We used two ML approaches: direct one, i.e. when ML model is trained to predict the structural parameters directly from the XANES spectrum and inverse one when ML model...
Article
The process of desorption of hydrogen from small palladium nanoparticles is monitored by time-resolved synchrotron X-ray diffraction. Changes in the diffraction patterns corresponding to the transition from the palladium β-phase to the α-phase are detected with an accuracy of 0.3 s. The model of the continuous change in the size of the β-phase regi...
Article
The data on the dynamics of structural changes in the composite cathode material based on iron(III) fluoride studied by the operando synchrotron X-ray spectroscopy and diffraction combined with the density functional theory (DFT) are reported. Based on the FeF3 structure determined by X-ray crystallography the crystal structure of LixFeF3 for 0 < x...
Article
Ab initio simulations of the pre-edge XAS spectra and other related resonance spectroscopies require taking into account 3d-4p hybridization on the 3d metal site. While the hybridization Hamiltonian could be parameterized on the basis of the symmetry of the system we introduce instead a set of 4p orbitals directly within the local Hamiltonian of th...
Article
Palladium-based catalysts are widely applied for the selective hydrogenation of acetylene in acetylene/ethylene mixtures. Under reaction conditions, palladium hydride or carbide phases can be formed, which change the catalytic properties of material. In the current work, we focus on the process of carbide phase formation in supported palladium nano...
Article
We have developed and tested cell for laboratory operando diagnostics of Li-ion cathode materials. Local atomic and electronic structure of LiFe1-xMnxPO4 olivine cathode was studied by means of Fe and Mn K-edges XAS and Mössbauer spectroscopy. Analysis of XAS data allows us to follow the structural and oxidation state changes occurring during the c...
Article
Functionalization of metal-organic frameworks with metal nanoparticles (NPs) is a promising way for producing advanced materials for catalytic applications. We present synthesis and in situ characterization of palladium NPs encapsulated inside functionalized UiO-67 metal-organic framework. The initial structure was synthesized with 10% of PdCl2bpyd...
Article
Formation of palladium hydride and carbide phases in palladium-based catalysts is a critical process which changes the catalytic performance and selectivity of the catalysts in important industrial reactions, such as selective hydrogenation of alkynes or alkadienes. We present a comprehensive study of a 5 wt.% carbon supported Pd nanoparticles (NPs...
Article
A colloidal solution of gold nanoparticles is synthesized with the use of sodium tetrachloroaurate(III) as a precursor, oleylamine as a reducer and surfactant, and 1-octadecene as a solvent. Reaction stages are analyzed in situ by optical (UV-vis) absorption spectroscopy with a simultaneous analysis of particle sizes by dynamic light scattering and...
Article
Full-text available
By means of symmetry analysis, density functional theory calculations, and Monte Carlo simulations we show that goethite, alpha-FeOOH, is a linear magnetoelectric below its Neel temperature T_N=400 K. The experimentally observed magnetic field induced spin-flop phase transition results in either change of direction of electric polarization or its s...
Article
Full-text available
By means of symmetry analysis, density functional theory calculations, and Monte Carlo simulations we show that goethite, $\alpha$-FeOOH, is a linear magnetoelectric below its N\'{e}el temperature $T_{\rm N}=400$ K. The experimentally observed magnetic field induced spin-flop phase transition results in either change of direction of electric polari...
Article
The exceptional thermal and chemical stability of UiO-66, -67 and -68 class of isostructural MOFs [J. Am. Chem. Soc., 2008, 130, 13850] makes them ideal materials for functionalization purposes aimed in introducing active centres for potential application in heterogeneous catalysis. We previously demonstrated that a small fraction (up to 10%) of th...
Article
Full-text available
Multilayered nanostructures (MN) were prepared by ion-beam successive sputtering from two targets, one of which was a metallic Co45Fe45Zr10 alloy plate and another target was a quartz (SiO2) or silicon plate on the surface of a rotating glass-ceramic substrate in an argon atmosphere. The Co and Fe K edges X-ray absorption fine structure of XANES in...

## Citations

... XAS signals obtained from the Ni K-edge of these materials are shown in Figure 1a. These spectra depict a clear difference in the structures (rectangular region) which are due to the different coordination environment of Ni ions with the nearest neighbor (Guda et al., 2021). The oxidation state of Ni ions in LiNiO2 materials is probed by comparing the XANES spectrum to that of Ni and NiO (Figure 1b). ...
... In addition to NN-based methods, other ML methods were also explored. For example, an Extra Trees regressor algorithm was applied to enhance the ability to fit EXAFS spectra with multiple scattering paths; 289 and an evolutionary algorithm method was employed to automate EXAFS analysis, with a goal of enhancing reliability and reproducibility of results. 290 These ML methods can provide statistical correlation among diverse configurations, more flexible analysis, and better interpretability, which is suitable for analyzing XAFS data for dilute alloys. ...
... Based on the size, shape, and aspect ratio (gold nanorods), spectral properties such as bandwidth and position of the SPR can be determined [86]. Pashkov et al. used direct and inverse ML approaches for training and elucidating the complex dependencies in the SPR spectra of Au-NPs and structural properties [87]. They trained the ML algorithm to predict SPR spectra for the given structural parameters and the structural parameters for the given spectral parameters. ...
... From these standpoints, of molecular devices are being actively studied and elaborated [1][2][3][4][5][6]. From these standpoints, supramolecular systems based on transition metal complexes with redox-active ligands, which are capable of reversible redox-isomer switching due to intramolecular electron transfer, become one of the most interesting objects [7][8][9]. Such switches are commonly regarded as a special case of valence tautomerism. ...
... The innovative development of these companies is currently relevant and promising in the world [1]. One of the main precise methods for studying nanocatalysts are in situ/operando methods using synchrotron radiation [2]. In this case, the key objects of interest are the local geometric and electronic structures of the material. ...
... The Osseo-Ti scaffold is manufactured using SLS of Ti-6Al-4V powder, based directly on 3D scans of cancellous bone and exhibits ~70% porosity and Laser Profilometry. All of these methods are widely studied and documented in literature for this purpose [211][212][213][214][215][216][217][218] and are summarised as follows. ...
... However, beyond atom and bond features, encoding more sophisticated structural information can be helpful or even required for accurate prediction of certain properties. For example, the bond angle information is necessary for correctly capturing electronic structure and bond hybridization [7][8][9][10] . Likewise, for the development of machine learning potentials where accurate energy prediction is needed, three-body (bond angle) and higher-order terms are often required to be included in the descriptor 11-13 . ...
... In the previous works, we explained such behavior by a gradual evolution of the cell parameters in the surface region of Pd nanoparticles (NPs) [5,15]. Different theoretical models were suggested as descriptive of the structure of palladium particles during formation and decomposition of hydrides [4,[16][17][18][19]. In particular, the core-shell structures were suggested [18]. ...
... In the recent works of Bowker [29][30][31], it was highlighted that under industrially relevant pressures on real catalysts, the processes are different from that on ideal surfaces and high-vacuum conditions, which are typical for surface science studies. In addition, palladium can easily form carbide phase in the presence of hydrocarbons [29,[31][32][33][34][35][36][37][38][39][40][41][42][43], which affects its catalytic properties. For this reason, the application of bulk-sensitive structural methods in addition to surface-sensitive ones is important to understand the structural evolution of the metal. ...
... More recently, Shapovalov et al. developed and tested the laboratory cell using operando Mö ssbauer and XANES for the LiFe 0.5 Mn 0.5 PO 4 cathode. 50 The results obtained from Mö ssbauer measurements indicated that the Fe and Mn ions distributed homogeneously and that the structural variations around Mn influenced the iron coordination. ...