Marina Shelyapina

Saint Petersburg State University | SPBU · Deaprtment of Nuclear Physics Research Methods

The local ordering and features of the molecular mobility of water confined in voids of a pure silica mordenite was studied using the molecular dynamics simulation over a temperature range from 298 to 163 K. The simulated system was a fragment of mordenite consisted of 2×2×4 unit cells filled with 384 water molecules. Three different water models:...

Adsorption of various glycerol conformations at Brønsted sites in mordenite is studied by the density functional theory. It is shown that the adsorption energy depends on the initial confor-mation of the glycerol molecule and ranges from –44.0 kcal/mol (beta-beta conformation) to –64.7 kcal/mol (alpha-gamma conformation). In some cases, the glycero...

Here, we report the results of our 1H nuclear magnetic resonance study of the dynamics of water molecules confined in zeolites (mordenite and ZSM-5 structures) with hierarchical porosity (micropores in zeolite lamella and mesopores formed by amorphous SiO2 in the inter-lamellar space). 1H nuclear magnetic resonance (NMR) spectra show that water exp...

The dynamics of H2O molecules confined in mesopores of about 3.4 nm in size, formed by amorphous SiO2 pillars separating 2D mordenite nanolayers, was probed by ¹H nuclear magnetic relaxation. ¹H nuclear magnetic resonance (NMR) spectra evidence the presence of water with different local surroundings and mobility. The temperature dependence of ¹H sp...

Mordenites are widely used in catalysis and environmental protection. The catalytic properties of mordenite are largely determined by the composition of its crystal framework, i.e., the SiO2/Al2O3 molar ratio (MR), and the cationic form. In H-mordenites, the most important characteristic becomes the structure and distribution of acid sites, which d...

Clinoptilolite is one of the most common, widespread and abundant zeolites in nature. Its availability, low cost, and outstanding ion exchange properties make clinoptilolite an excellent candidate for both direct use and various modifications to create new low-cost functional materials for sustainable development. Specific applications in which cli...

The electronic properties of various cationic forms of MFI type lamellar zeolites were studied using DFT calculations and compared with their bulk counterparts. In this study, Na⁺ and H⁺ cations were considered for the effect of charge deficit compensation on the surface of lamellar zeolites. The results show that lamellar zeolites in different cat...

New TiO2/2D mordenite nanocomposites were synthetized from lamellar mordenite by introduction of titanium tetraetoxide (TEOT) into the interlamellar space with further hydrolysis and calcination. Anatase nanoparticles with an average size of 4 nm form pillars separating mordenite layers, creating mesoporosity. The surface area, pore size distributi...

Hydrogen is an energy carrier that can be a sustainable solution for alternative energy with zero greenhouse gas emissions. Hydrogen storage is a key point for hydrogen energy. Metals provide an access for safe, controlled and reversible hydrogen storage and release. Magnesium, due to its outstanding hydrogen storage capacity, high natural abundanc...

Two samples of protonated mordenite with close nominal molar ratios (MRs) SiO2/Al2O3 equal to 15.0 and 15.2 are studied by various physicochemical methods. Both samples have the mordenite crystal structure but different morphologies and exhibit different dehydration patterns. According to the ¹H, ²⁷Al, ²⁹Si NMR data, these samples show different lo...

Water embedded in the crystal structure of a solid hydrate may affect the functional properties of the material. A decisive step towards understanding the role of water in the restricted geometry is to unravel the arrangement and dynamics of water molecules. The paper attacks this issue using the example of NaBiO3–based material containing at ambie...

Long-term changes in species of copper-silver bimetallic systems on natural clinoptilolite obtained by ion exchange of Cu2+ and Ag+ and then reduced at different temperatures were studied. Even after storage under ambient conditions, XRD and UV-Vis diffuse reflectance spectra indicate the presence of nanospecies and larger particles of reduced copp...

On the basis of the density functional theory (DFT) calculations, the successive isomorphic substitution of one to six tetrahedrally coordinated Si cations by trivalent Al was systematically studied. As a result of exploring a significant number of configurations, without using a priori assumptions, it was found that the Al atoms are accommodated a...

The photocatalytic activity of layered perovskite-like oxides in water splitting reaction is dependent on the hydration level and species located in the interlayer slab: simple or complex cations as well as hydrogen-bonded or non-hydrogen-bonded H2O. To study proton localization and dynamics in the HCa2Nb3O10·yH2O photocatalyst with different hydra...

The electronic properties of LTA-type zeolites in their siliceous, aluminized, and ferric frameworks compositions, all of which were selected in their sodium ion-exchange form and under anhydrous conditions, were studied through DFT computations. In the case of an aluminized framework, it was found that the non-Löwensteinian configuration is not on...

Cuban and Mexican zeolites are of particular interest from economic outlook because of their exceptional properties and abundance. Here, we present the results of the comparative study of the elemental, structural, morphological, thermal and textural properties of natural zeolites: clinoptilolite, mordenite and erionite from various deposits. Despi...

Emerging technologies aimed to tune properties of microporous materials, including zeolitic catalysts, involve microwave processing that accelerates chemical reactions and often increases efficiency of target materials. Here we report on the results of our comprehensive study of copper-exchanged mordenites obtained from sodium mordenite with Si/Al...

The protonated perovskite-like titanate H2La2Ti3O10 has been used to produce organic-inorganic hybrids with simple organic molecules: methylamine, methanol, monoethanolamine, and n-butylamine. The optimal pathways for the preparation of such hybrids are summarized. Solid-state NMR, combined with thermal analysis, Raman, and IR spectroscopy, has bee...

Mesostructured pillared zeolite materials in the form of lamellar phases with a crystal structure of mordenite (MOR) and ZSM-5 (MFI) were grown using CTAB as an agent that creates mesopores, in a one-pot synthesis; then into the CTAB layers separating the 2D zeolite plates were introduced by diffusion the TEOS molecules which were further hydrolyze...

Industrial development and urbanization require effective constant monitoring and effective removal of major air pollutants. Three of them, the fight against which is discussed in this chapter, appear in the process of burning fuel, although their genesis is different. Sulfur oxide is formed as a result of the combustion of impurities either in hyd...

Ti-V-based body-centered cubic (BCC) alloys have potential for large-scale hydrogen storage if expensive vanadium is substituted with much cheaper Fe-containing ferrovanadium. Use of ferrovanadium reduces the alloys’ hydrogen storage capacity. This is puzzling since the amount of Fe is low and hydrogen atoms are accommodated in interstitial sites w...

As it was reported in our previous study (P. Sánchez-López et al., 2019), mono- and bimetallic systems of Ag, Fe, and Ag-Fe supported on mordenites exhibit a nontrivial dependence of deNOx activity from the preparation procedure. In this work we report on the results of our comprehensive study of the sample composition, structure and morphology to...

In order to optimize hydrogen storage properties of bcc Ti-V-Cr alloys it was found that alloying with a few 4 at% of Zr7Ni10 results in acceleration the hydrogen sorption kinetics in the composite material. The novel intergranular phase plays a role of gate for hydrogen, leading parallel to its easy decrepitate, thus enhancing fast formation of Ti...

The set of copper-exchanged mordenites with variations in Si/Al atomic ratio (6.5 and 10) and exchangeable counter-cations (Na⁺, [NH4]⁺, H⁺) prepared by different methods (conventional and microwave assisted), has been studied. Application of nondestructive analytical methods with different depth vision, such as EDS and XPS, simultaneously with the...

This review deals with the destabilization methods for improvement of storage properties of metal hydrides. Both theoretical and experimental approaches were used to point out the influence of various types of defects on structure and stability of hydrides. As a case study, Mg, and Ni based hydrides has been investigated. Theoretical studies, mainl...

A series of (TiCr1.8)1-xVx alloys with x = 0.2, 0.4, 0.6 and 0.8 was synthetized by induction melting of a mixture of TiCr1.8 alloy and pure V. It has been found that after hydrogenation all the compounds turn into bct structure. The present bct metal hydrides could be considered forming a pre-martensite state during the transformation (Ti-V-Cr)Hxm...

Hydrogen diffusion and solubility in disordered alloys are of paramount importance to a variety of practical applications from hydrogen storage materials to separation membranes and protection against hydrogen embrittlement. By employing density functional theory calculations we unveil the atomic-level understanding of hydrogen diffusion in disorde...

Copper-exchanged mordenites prepared by different methods, conventional and microwave assisted, have been investigated by TG, DSC, temperature-programmed reduction (TPR), and EPR methods. TPR study of hydrated and annealed at 573 and 973 K samples revealed that the copper reduction occurs directly from Cu2+ to Cu0, and Cu2+ ions are in different lo...

Comprehensive research of water behavior in Na- and Cu-mordenites with different Na/Cu ratio was done. Several steps of dehydration process were detected and analyzed, taking into account difference in chemical composition of the samples, reaction models and corresponding kinetic equations. Activation energies for these steps were calculated. It wa...

Problem of hydrogen storage is a key point for the extensive use of hydrogen as an energy carrier. Metal hydrides provide a safe and very often reversible way to store energy that can be accessed after hydrogen release and its further oxidation. To be economically feasible, the metal or alloy used for hydrogen storage has to exhibit high hydrogen s...

Ti–V–Cr alloys are hydrogen storage materials, but their characteristics, which are important for practical applications, depend strongly on composition. The search for an optimal composition with given characteristics requires the support of theoretical calculations of the electronic structure of alloys and their hydrides. In this paper, the inter...

Sodium mordenite was Cu²⁺-exchanged by conventional methods at ambient temperature (accepted as 20 °C) and with microwave radiation at 100 ± 1 °C. To increase the copper content, we repeat the exchange procedure several times. Both the degree of Cu²⁺ exchange and the environment of the Cu²⁺ ions depend on the method of exchange. Neither conventiona...

Samples of mordenites with variable Si/Al atomic ratio and different counter-ions were exchanged with copper ions by two methods – the conventional treatment in water solution and by microwave-assisted procedure. The zeolite-solution ratio and the concentration of solution were kept equal for both procedures. We report on the results of XRD, TGA an...

Here we report on the results of our theoretical study of 1H-MoS2 clusters grown on graphene oxide. First, we studied graphene cluster, graphene oxide (1,2) and (1,3) ether-like monolayers with a Stone-Wales defect. Secondly, a 1H-MoS2 nanoparticle was grown over the defect creating a sandwich like structure. For all considered structures energy ba...

Ion-exchange zeolites are the starting materials for the synthesis of nanocomposites. Moreover, they are of great interest in themselves, because cations in zeolites, and especially cations of transition metals, are the active catalytic sites. Copper-exchange zeolites are known as very effective deNOx catalysts. Although these compounds have been e...

Studies of interstitial hydrogen diffusion play a key role in understanding of fundamental properties of hydrogen storage materials since the activation energy required to jump from one interstitial site to another affects both the hydrogen sorption kinetics and the desorption temperature. Nuclear magnetic resonance is a very effective tool to stud...

To describe microscopic hydrogen migration processes and steps of hydride formation we have carried out a theoretical study of the hydrogen diffusion in hexagonal closed packed (hcp), body-centered cubic (bcc), and face-centered cubic (fcc) Mg-lattices. To determine the preferable hydrogen diffusion pathways the activation energy Ea along the minim...

Here we propose an improved exchange model of proton relaxation to describe hydrogen mobility in intermetallic hydrides. The model has been successfully applied to a number of hydrides of ternary Ti–V–Cr alloys of different composition, namely, TiV0.8Cr1.2, Ti0.5V1.9Cr0.6 and Ti0.5V1.9Cr0.6 + 4 wt.% Zr7Ni10. It has been found that (i) there are two...

Here we report on the results of proton NMR study of hydrogen self-diffusion in hydrides of Ti–V–Cr alloys of different composition, pure and with 4 wt.% of Zr7Ni10 additives, namely, TiV0.8Cr1.2H5.29, Ti0.5V1.9Cr0.6H5.03 and Ti0.33V1.27Cr1.4H1.13. The measurements have been made using the static field gradient nuclear magnetic resonance technique....

Absorption or emission of energy by quantum systems as a result of their interaction with an electromagnetic field is the basis of all of the methods of quantum radio physics.

Nuclear magnetic resonance in magnetically ordered materials was first observed by Gossard and Portis in the metallic cobalt on \(^{59}\)Co nuclei A. C. Gossard and A. M. Portis, Observation of Nuclear Resonance in a Ferromagnet. Phys. Rev. Lett. 3 (1959) 164–166. Since then numerous studies of different magnetically ordered materials were performe...

The analysis of the nature of splitting of ion levels under the influence of the crystal field is based on the Wigner theorem and Eq. 10. 30.

A very important aspect of the physics of magnetic resonance are so-called double resonances. The essence of the double resonance experiments consists in the influence on the selected spin resonance transition with continuous or pulsed alternating magnetic field and the registration of the response at another transition in the same or another spin...

In isotropic liquids there are relatively fast rotational and translational movements of molecules.

As we might expect, for the observation of NMR it is required permanent magnetic field \(\vec {B}_0\), in which the Zeeman splitting of energy levels of the spin system is realized, and a alternating radio frequency field \(\vec {B}_1\), stimulating transitions between the Zeeman sublevels.

As it was already mentioned in Sect. 1. 11, interactions between electron and nuclear magnetic momenta are termed as hyperfine interactions (HFI)

One of the applications of Quantum Radiophysics is quantum magnetometry, based on the phenomenon of magnetic resonance and optical orientation atomic and nuclear moments. Specialists in many fields of physics and engineering face the necessity of the magnetic measurements, but the long-known classical methods do not provide modern requirements to a...

Liquid crystal or mesophase is a thermodynamic phase of matter which differs from isotropic liquids and single crystals.

Already in the first papers on the ammonia maser, it was stated that if the self-excitation condition is not satisfied, the device can serve as an amplifier of microwave power with low intrinsic noises. This is due to the fact that the probability of spontaneous emission in the radio diapason is very low and noises of an amplifier are determined on...

For the realization of the process of quantum amplification of electromagnetic waves it is necessary to create an anomalous difference the populations of energy levels: the population of the upper level must be greater than the lower one (see Sect. 17. 1). More over, it was shown in Sect. 3. 2, that it is impossible to create such stationary state...

In Chap. 1 the concepts of the nuclear magnetic relaxation times (rates) were introduced on the basis of phenomenological considerations, as exemplified by the theory of Bloch.

As it was already mentioned in Chap. 11, a main factor defining the structure of spectra of the electron paramagnetic resonance is the interaction of electrons with the nearest molecular environment and nuclei of atoms and the molecules forming a paramagnetic center.

Nuclear quadrupole resonance (NQR) is one of the most sensible tools to study the local structure of materials, electronic density distributions near the nuclei under study, the nature of defects in solids, the mobility of molecules, or their parts, phase transitions and so on. It is very helpful to investigate physical properties of solids, molecu...

Application of the NMR methods to solids provides much more information than for liquids or gases. The matter is that interactions, which determine NMR spectra of solids, in contrast to interactions in liquids, keep anisotropic properties. The main interactions are dipole–dipole interactions, quadrupole interactions, and interactions of nuclear mag...

We have already met the situations when the crystal field model does not lead to correct results. This is the case of the strong crystal field when the interaction of surrounding ions or molecules with a paramagnetic center is comparable with electrostatic interactions of electrons in a ion.

This part focuses the attention on the approach suitable for studying assemblies of weakly interacting paramagnetic centers. Here we will not consider magnetically ordered systems where ferromagnetic, ferrimagnetic or antiferromagnetic resonance phenomena can be observed, as well as systems with free electrons (metals and semiconductors).

In nuclear quadrupole resonance, splitting of energy levels of a spin system occurs under the influence of the interaction between the nuclear quadrupole moment and intracrystalline electric field gradients. That allows us to observe NMR signals in zero or weak static magnetic field. The absence of electromagnets essentially decreases the necessary...

In this and follow-up chapters we will describe the physical principles for the development of devices, in which an element that determines their properties is an ensemble of micro-particles (nuclei, atoms, molecules, and so on) in special state. In the classical radioelectronics, there are numerous devices that use the so-called narrow-band elemen...

At present, there are both active and passive devices of the quantum radioelectronics, in which to increase the intensity of a spectral line in the radio diapason one uses an auxiliary radiation of optical range.

Two-dimensional Fourier-transform spectroscopy of nuclear magnetic resonance is one of the capital and most extensive research concepts in the NMR spectroscopy that allows the investigation of complex systems of coupled nuclear spins. Usual one-dimensional spectra are failed to be decoded because of inevitable lineoverlap for large molecules.

The book is devoted to the description of the fundamentals in the area of magnetic resonance. The book covers two domains: radiospectroscopy and quantum radioelectronics. Radiospectroscopy comprises nuclear magnetic resonance , electron paramagnetic resonance, nuclear quadrupolar resonance, and some other phenomena. The radiospectroscopic methods a...

Here we report results of Ab initio calculations on phase transitions in bulk magnesium, as well as those occurring upon hydrogenation. The calculations have been carried out within the framework of the FLAPW method. Possible pathways of hydrogen induced phase transitions are discussed.

Combined self-propagating high-temperature synthesis and hydride cycling methods form a novel and recently developed technique allowing preparing specific multiple-phase materials. Ternary Laves phase related to bcc solid solution and binary bcc V-Ti alloys and their hydrides were prepared using this route. In this report, the microstructure and hy...

This paper reports on the results of theoretical investigations carried out for the hydrides Mg2FeH6 and Mg2CoH5 and the mixed hydride Mg2(FeH6)0.5(CoH5)0.5 in terms of the full-potential linearized augmented plane wave (FLAPW) method. It has been shown that the partial substitution of the Co atoms for the Fe atoms leads to a slight increase in the...

Magnetite is a very promising candidate for hard electrode in magnetic tunnel junction devices due to its electronic and magnetic properties. Addition of a buffer iron layer improves required properties. Here we report on the results of our DFT study of the impact of the additional Fe buffer layer on the electronic and magnetic properties of magnet...

According to H-1 NMR study in fcc hydrides of disordered Ti-V alloys hydrogen atoms are distributed over both octahedral and tetrahedral sites. The occupancy of octahedral sites increases with the vanadium concentration. In hydrides of ternary Ti-V-Cr alloys hydrogen atoms occupy tetrahedral sites only.

In this contribution we report on the results of our recent 1H NMR studies of different metal hydrides of interest for reversible hydrogen storage applications: Ti–V–Cr alloys of various compositions, pure and with Zr7Ni10 or Hf7Ni10 additives, and in additives themselves. The temperature dependences of 1H spin-lattice relaxation have been treated...

Mg/TM thin films are objects of interest as hydrogen storage materials due to their expected interesting thermodynamic and hydrogen sorption kinetic properties. Here we report on the results of ab initio calculation on the stability of Mgn/Ti and Mgn/Nbm thin films.

Occurrence of phase transitions in TixVyCrz-H systems was analyzed versus temperature. Hydrogen evacuates from the hydrogenated compounds via two main steps. The 1st step corresponds to the destabilization of the fcc hydrogenated lattice leading to a fcc → bcc martensitic type transformation. The 2nd step occurs according to the decomposition of th...

During the last decades hydrogen has attracted worldwide attention as an energy carrier. MgH2 is one of the most promising materials for hydrogen storage due to its high hydrogen uptake, large reserves and low cost. However, the potential for practical use of MgH2 is severely limited because of its high temperature of hydrogen discharge, slow desor...

Titanium-vanadium-chromium alloys are promising materials for hydrogen storage. They can absorb up to 3.8 wt % of hydrogen with a variable (depending on the composition) temperature of hydrogen release in a convenient range. This paper reports on the results of investigations of the TiV0.80Cr1.20H5.29 hydride by continuous-wave (cw) and pulsed 1H n...

The experimental frequency and temperature dependences of proton spin-lattice relaxation in metallic hydrides are often treated within the Bloembergen-Purcell-Pound model. However, even the consideration of activation energy (or correlation time) distribution does not provide a satisfactory agreement with experimental data. It was experimentally de...

The influence of Al and Zn atoms on the stability of the Mg7Ti compound and its hydride Mg7TiH16 has been studied theoretically. The calculations have been carried out in terms of the full-potential linearized augmented plane wave method. It has been demonstrated that the partial substitution of Al or Zn atoms for magnesium atoms leads to a decreas...

This paper reports on the results of the theoretical investigation of magnesium hydride nanoclusters doped with 3d metals (from Sc to Zn). The influence of transition metal atoms on the geometry, electronic structure, and energy characteristics of the clusters has been analyzed. The results of the performed calculations have been compared with the...

MgH2 is one of the most promising materials for hydrogen storage. However, its rather slow hydrogen absorption and desorption kinetics and high dissociation temperature essentially limit its application in this field. Nevertheless mixing Mg or MgH2 with small amount of transition metals or their oxides remarkably accelerates the hydrogen kinetics....

We report on the study of (MgH2)n + M complexes (M = Ti or Ni) carried out within the framework of the cluster density functional theory (DFT) method. The influence of such transition metal atoms on the cluster geometry and electronic structure is discussed considering the stability of MgH2 hydride.

The magnetic properties of Fe1 − x Cox B and (Fe1 − x Cox )2B disordered compounds were investigated using first-principles calculations of the electronic structure in the framework of the density functional theory with the Korringa-Kohn-Rostoker method. The concentration dependences of the magnetic moments and the electron density were calculated...

Hydrogenation and desorption of the bcc compound Ti0.5Cr0.6V1.9 was sequentially followed in the course of a time-resolved in situ neutron diffraction experiment on the D20 high flux diffractometer at the Institut Laue Langevin, Grenoble.From the structural point of view it has been shown that hydrogenation induces a structural type of transformati...

A high concentration of the acceptor impurities (NA about of 1020 cm−3) influence on the electronic structure, the Fermi level location, electro-conductivity, Seebeck coefficient, and magnetic susceptibility in the n-ZrNiSn intermetallic semiconductors was investigated. An importance of both donor and acceptor impurity bands in the heavy-doped n-Zr...

The electronic structure of Ti-V-Cr alloys is calculated using the Korringa-Kohn-Rostoker method in the coherent potential approximation. The phase stability of the alloys is investigated as a function of the stoichiometry, the composition, and the hydrogen concentration. The results obtained are in good agreement with the available experimental da...

A condition for attaining the maximum values of thermoelectric power Z* in intermetallic semiconductors of the MgAgAs structural type consists in heavy doping of these semiconductors with donor and/or acceptor impurities with concentrations at which the Fermi level is pinned at the mobility threshold for the corresponding band of continuous energie...

The role of the donor impurity band in the conduction of highly doped and compensated intermetallic semiconductors with MgAgAs type of structure was investigated. A simulation of the electronic structure for TiCo1−xNixSb semiconducting solid solution was carried out. A scheme of the impurity band transformation in TiCoSb semiconductor due to donor...

The electric field gradient (EFG) tensor at the aluminum nucleus sites in yttrium-aluminum garnet Y3Al5O12 is calculated using the Hartree-Fock method and the nonempirical cluster approach. It is shown that the EFG tensor at the Al-tetr sites is described well taking into account the nearest neighbors (an [AlO4](-5) cluster), whereas for the Al-oct...

The role of the impurity donor band in the conductivity of the heavily doped and compensated intermetallic TiCoSb semiconductor is determined. The electronic structure of the TiCo1–x NixSb semiconductor alloy is calculated. A model of impurity band transformation in the TiCoSb semiconductor due to donor impurity doping is suggested. The transition...

The Korringa-Kohn-Rostoker Green's function method within the coherent-potential approximation was applied to calculate the electronic properties of recently synthesised semi-Heusler TiCo1-xNixSb solid solution. As evidenced parallel from electrical resistivity measurements, the calculations confirm a semiconductor type behaviour for TiCoSb compoun...

We report here on a theoretical study of the stability and the electronic structure of Ti‐V‐Cr ternary compounds and their related hydrides. The total energy and electronic structure were calculated using the spin‐polarised Korringa‐Kohn‐Rostoker method combined with coherent‐potential‐approximation. First, we have studied the stability of differen...

In this paper, we report on calculations of the electronic structure and the magnetic coupling in Fe1-xCoxB and (Fe1-xCox)2B iron cobalt borides. In Fe1-xCoxB, the atomic magnetic moments decrease versus x the Co concentration and a ferromagnetic nonmagnetic phase transition occurs at x˜0.9. For this series, our calculations show the presence of a...

The periodic Hartree–Fock method has been applied to calculate the electronic structure of the yttrium aluminium garnet. We report on the results of the density of state calculations, the population analysis, as well as the electric-field-gradient distribution. A comparative analysis with the related structure α-Al2O3 was done. The calculations sho...

The role of the impurity acceptor band in the conductivity of the doped and compensated ZrNiSn semiconductor is assessed. A reconstruction model of the impurity band as a result of doping the semiconductor with acceptor impurities is suggested. The electronic structure of the Zr1−x ScxNiSn alloy is calculated. Oscillations of the magnetic susceptib...