Research Interests:
Поиск в библиотеке, Расширенный поиск. ...
Research Interests:
On the basis of statistical thermodynamic model of clathrate hydrates, the existence of helium clathrate hydrates of cubic structures I (sI), II (sII) and helium hydrate based on the framework of ice II has been predicted and their... more
On the basis of statistical thermodynamic model of clathrate hydrates, the existence of helium clathrate hydrates of cubic structures I (sI), II (sII) and helium hydrate based on the framework of ice II has been predicted and their formation pressures have been estimated. We employ here the quasiharmonic lattice dynamics method in order to estimate free energy and Gibbs free energy of helium clathrate hydrates sI, sII and helium-filled ice II. This method allows one to examine hydrates of different structures with multiple occupancies of cages by helium and so to establish the conditions for stable multiple occupancy. The method permits also to estimate the chemical potentials of guest and host molecules. On the molecular level the curves of monovariant equilibrium ‘gas phase-helium clathrate hydrate(helium-filled ice II)-ice (water)’ and the degree of filling of the large and small cavities for hydrates sI, sII and helium-filled ice II in a wide range of pressure and temperature ha...
A method for studying the time dependence of the short-range molecular order of water has been proposed. In the present study, water is considered as a dynamic network between molecules at distances not exceeding 3.2 Å. The instantaneous... more
A method for studying the time dependence of the short-range molecular order of water has been proposed. In the present study, water is considered as a dynamic network between molecules at distances not exceeding 3.2 Å. The instantaneous configurations obtained with the molecular dynamics method have been sequentially analyzed. The mutual orientation of each molecule with its neighboring molecules has been studied and the interaction energy of each pair of neighbor molecules has been calculated. The majority of mutual orientation angles between molecules lie in the interval [0°; 20°]. More than 85% of the molecular pairs in each instantaneous configuration form H-bonds and the H-bond network includes all water molecules in the temperature range 233–293 K. The number of H-bonds fluctuates near the mean value and increases with decreasing temperature, and the energy of the vast majority of such bonds is much higher than the thermal energy. The interaction energy of 80% of the H-bondin...
Research Interests:
In this contribution, a method based on a solid solution theory of clathrate hydrate for multiple cage occupancy, host lattice relaxation, and guest-guest interactions is presented to estimate hydrate formation conditions of binary and... more
In this contribution, a method based on a solid solution theory of clathrate hydrate for multiple cage occupancy, host lattice relaxation, and guest-guest interactions is presented to estimate hydrate formation conditions of binary and ternary gas mixtures. We performed molecular modeling of the structure, guest distribution, and hydrate formation conditions for the CO2 + CH4 and CO2 + CH4 + N2 gas hydrates. In all considered systems with and without N2, at high and medium content of CO2 in the gas phase, we found that CO2 was more favorable in occupying clathrate hydrate cavities than CH4 or N2. The addition of N2 to the gas phase increased the ratio concentration of CO2 in comparison with the concentration of CH4 in clathrate hydrates and made gas replacement more effective. The mole fraction of CO2 in the CO2 + CH4 + N2 gas hydrate rapidly increased with the growth of its content in the gas phase, and the formation pressure of the CO2 + CH4 + N2 gas hydrate rose in comparison to ...
Research Interests:
Nature is the international weekly journal of science: a magazine style journal that publishes full-length research papers in all disciplines of science, as well as News and Views, reviews, news, features, commentaries, web focuses and... more
Nature is the international weekly journal of science: a magazine style journal that publishes full-length research papers in all disciplines of science, as well as News and Views, reviews, news, features, commentaries, web focuses and more, covering all branches of science and ...
Research Interests:
Research Interests:
Research Interests:
ABSTRACT
Research Interests:
This article is a review of our papers devoted to the application of the Lifshitz, Dzjaloshinskii, Pitaevskii theory for the theoretical investigation of the thermodynamical properties of the plane, spherical and cylindrical interfaces... more
This article is a review of our papers devoted to the application of the Lifshitz, Dzjaloshinskii, Pitaevskii theory for the theoretical investigation of the thermodynamical properties of the plane, spherical and cylindrical interfaces and layers. In accordance with this theory the thermodynamical properties of the surface are determined by the fluctuating electromagnetic field. This field may be characterized by the averaged quadratic combinations of the electric and magnetic strength which are thermodynamical Green functions of this field. We have obtained these Green functions for the spherical and cylindrical interfaces and applied them for the calculations of the different thermodynamical quantities such as electromagnetic stress tensor, chemical potential, and density variation. We have shown that, in general, it is not valid to obtain size and form dependence of the thermodynamical quantities by using two-particle Van der Waals potential. We discuss the surface tension depend...
Research Interests:
ABSTRACT
Research Interests:
ABSTRACT
Research Interests:
Storage of hydrogen as hydrogen hydrate is a promising alternative technology to liquefied hydrogen at cryogenic temperatures or compressed hydrogen at high pressures. In this paper, computer simulation is performed based on the solid... more
Storage of hydrogen as hydrogen hydrate is a promising alternative technology to liquefied hydrogen at cryogenic temperatures or compressed hydrogen at high pressures. In this paper, computer simulation is performed based on the solid solution theory of clathrates of van der Waals and Platteeuw with some modifications that include in particular the account of multiple cage occupancies and host relaxation. The quasiharmonic lattice dynamics method employed here gives the free energy of clathrate hydrate to first order in the anharmonicity of intermolecular potential and permits to take into account quantum zero-point vibration of host lattice and hydrogen in the cages. It is employed to study the thermodynamic functions of binary (mixed) H 2– CH 4 hydrates of cubic structure II (sII) and hexagonal structure H (sH). It is shown that at divariant equilibrium "gas phase–gas hydrate" with increasing pressure the filling of large cavities by hydrogen proceeds gradually from sing...
Research Interests:
ABSTRACT
Research Interests:
A model of interatomic interactions of Tl2CaBa2Cu2O8 , which takes into account coulombic interaction and covalent bonds, is presented. Vibrational spectrum is calculated using that model, and a comparison with experiments on Raman... more
A model of interatomic interactions of Tl2CaBa2Cu2O8 , which takes into account coulombic interaction and covalent bonds, is presented. Vibrational spectrum is calculated using that model, and a comparison with experiments on Raman scattering is given.
Research Interests:
ABSTRACT
Research Interests:
Research Interests:
Urotropine-based porous coordination polymers with free N-donors demonstrate selective adsorption towards acidic gas substrates (C2H2 or CO2) as confirmed by isotherm measurements and ab initio DFT calculations.
Research Interests:
Dynamic properties of low (LDA), high (HDA) and very high (VHDA) density amorphous ices were investigated within the approach based on Lattice Dynamics simulations. In this approach, we assume that the short-range molecular order mainly... more
Dynamic properties of low (LDA), high (HDA) and very high (VHDA) density amorphous ices were investigated within the approach based on Lattice Dynamics simulations. In this approach, we assume that the short-range molecular order mainly determines the dynamic and thermodynamic properties of amorphous ices. Simulation cell of 512 water molecules with periodical boundary conditions and disordering allows us to study dynamical properties and dispersion curves in the Brillouin zone of pseudo-crystal. Existence of collective phenomena in amorphous ices which is usual for crystals but anomalous for disordered phase was confirmed in our simulations. Molecule amplitudes of delocalized (collective) as well as localized vibrations have been considered.
Solvation behavior of task-specific ionic liquids (TSILs) containing a common, L-histidine derived imidazolium cation [C20H28N3O3]+ and different anions, bromide-[Br]- and bis(trifluoromethylsulfonyl)amide- [NTF2]- in water is examined,... more
Solvation behavior of task-specific ionic liquids (TSILs) containing a common, L-histidine derived imidazolium cation [C20H28N3O3]+ and different anions, bromide-[Br]- and bis(trifluoromethylsulfonyl)amide- [NTF2]- in water is examined, computationally. These amino acid functionalized ionic liquids (ILs) are taken into account because of their ability to react with rare earth metal salts. It has been noted that the TSIL with [Br]- is more soluble than its counterpart TSIL with [NTF2]-, experimentally. In this theoretical work, the combined classical molecular dynamics (CMD) and density functional theory (DFT) calculations are performed to study the behavior of bulk phase of these two TSILs in the vicinity of water (H2O) molecules with different concentration. Initially, all the constructed systems are equilibrated using CMD method. The final structures of the equilibrated systems are extracted for DFT calculations. Under CMD operation, the radial distribution function (RDF) plots and viscosity of TSILs are analyzed to understand the effect of water on TSILs. In DFT regime, binding energy per H2O, charge transfer, charge density mapping and electronic density of states (EDOS) analyses are done. The CMD results along with the DFT results are consolidated to support the hydrophilic and hydrophobic nature of the TSILs. Interestingly, we have found a strong correlation between the viscosity and the EDOS results that leads to understand the hydration properties of the TSILs.
Research Interests:
ABSTRACT
Research Interests:
Research Interests:
A simple universal model of formation of clathrate crystal nuclei in solution is suggested. The model is applicable equally to all clathrate materials: gas hydrates, cage zeolites (clathrasils) and clathrate compounds of semiconductor... more
A simple universal model of formation of clathrate crystal nuclei in solution is suggested. The model is applicable equally to all clathrate materials: gas hydrates, cage zeolites (clathrasils) and clathrate compounds of semiconductor elements. The basic feature of the model is joining of polyhedral cage precursors, formed around guest molecules, by means of direct, or intermediated by one host molecule, bonds between precursors. The type of precursor cage formed in solution is determined strictly by the size of guest molecules. This defines the first link of the causal chain connecting the size of guest molecule and the clathrate structure formed. We name such cage precursors ‘structure-forming units‘ (SFU). For the structure I clathrates there are two SFU’s: small and large cage precursors, depending on the size of guest molecule, and, correspondingly, two routes of crystal growth. For other structures SFU is always the large cage. It is shown that for any clathrate structure there forms in solution correct dimer cluster of cage precursors corresponding to a pair of neighboring (without common faces) cages in the real clathrate crystal and no other (false) configurations forms. Consideration of initial growth stages after formation of the dimer clusters shows that growth in all cases can continue by usual mechanism of attaching single host molecules from solution with formation of new cages in the cluster. This growth is, in principle, unlimited and does not create defects. This means that structural information contained in cluster, even on the level of dimers, is sufficient for formation of the clathrate crystal by successive attachment of individual host molecules.
Research Interests:
Research Interests:
Research Interests:
Theoretical approach was developed for description of clathrate hydrates stability area at low and modestly high temperatures on molecular level. The approach permits to account for interactions between guest molecules and dependence of... more
Theoretical approach was developed for description of clathrate hydrates stability area at low and modestly high temperatures on molecular level. The approach permits to account for interactions between guest molecules and dependence of unit cell structure upon guest's sort, temperature and pressure. Non-ideality of the gas phase was accounted using Van-der-Waals equation of state. Within this approach, methane hydrate calculations have been performed both for low temperature and low pressure region (in equilibrium with ice Ih) and for modestly high temperatures and pressures (in equilibrium with liquid pure water). Calculations show the notable dependence of hydrates thermodynamic properties upon the guest-guest interactions. For methane hydrates, the guest-guest interaction energy can reach 10% of the guest-host value. The results of calculations are in good agreement with available experimental data. This method is applicable for accurate prediction of clathrate hydrate stabi...
Research Interests:
ABSTRACT