Imeni Vladimira Il'icha Lenina, Russia
Imeni Vladimira Il'icha Lenina, Russia

Time filter

Source Type

Gafner Yu.Ya.,Khakas State University | Gafner S.L.,Khakas State University | Redel L.V.,Khakas State University | Zamulin I.S.,Khakas State University | Samsonov V.M.,Tver State University
Journal of Computational and Theoretical Nanoscience | Year: 2015

Using molecular dynamics method and several different tight-binding potentials, the heat capacity of fcc palladium clusters of 6 nm in diameter has been investigated in the temperature range from 150 to 300 K. We have concluded from the results of our computer simulations that the heat capacity in the case of isolated free clusters can exceed that of a bulk material. At 150 K the values obtained for palladium nanoparticles exceed those of the corresponding bulk material by 12-16%. It was also found that the difference in question becomes less noticeable under growing the temperature. So, at 300 K the isobaric heat capacity of nanocrystalline palladium was only by 4-5% higher in comparison with the bulk phase. Consequently, the large heat capacities of palladium nanostructures observed in some real experiments cannot be related to the characteristics of free clusters. We hypothesize that these properties of a nanomaterial depend on the degree of agglomeration of its constituent particles, i.e., the surfaces and interphase boundaries of interconnected nanoclusters can have a strong effect. To test this hypothesis, we took metallic clusters of various sizes produced through the simulation of condensation from the gas phase. At high temperatures, we failed to adequately assess the role of the interphase boundaries in calculating the heat capacity of nanoparticles. The reason was the mass diffusion of atoms to impart an energetically more favorable shape and structure to the synthesized clusters. To explain the disagreement of our results with the available experimental data on compactificated palladium, additional investigations were carried out on palladium sample with the density corresponding to 80% of the bulk value. The possible role of hydrogen in the increase of the heat capacity observed for compacted palladium has been estimated. The conclusion, that the results, which are in satisfactory agreement with the experimental data, were obtained only when the concentration of hydrogen atoms accounted for approximately 50% of the concentration of palladium atoms has been drawn. In all probability, the nature of so significant overestimation of the heat capacity of compactificated nanomaterials relates both to their disordered state and, to some extent, to noticeable content of different dopes, mainly of hydrogen. Copyright © 2015 American Scientific Publishers.


Kurbanova E.D.,RAS Institute of Metallurgy | Polukhin V.A.,Ural Federal University | Chepkasov I.V.,Khakas State University
Letters on Materials | Year: 2016

Basing on molecular dynamics method the study of thermic evolution of 2D and 3D nanoclusters has been carried out. There has been revealed nature of generation and activation kinetic processes, initiated structure transformation and boosing the thermostability of functional unities of two dimentional transition metallic systems deposited on graphene and silicene substrates. Thus there has been formed by chemical bonds specific interfaces as functional unified low-dimentional systems. In the presented article results of the molecular and dynamic modeling executed with use of multiparticle potentials. There has been carried out the analysis the thermoactivity of processes of a relaxation, diffusion and formation of the interface structures metal / graphene (G) metal / silicene (Me: Ag, Ni, Al), their destruction, as analog of melting in low-dimensional systems. The diffusion components in the X-Y interface planes and the normal along axis Z for all considered Me/G systems depended differently on the heating temperature, reflecting the different natures of variations in the electron structure (adhesion energy and the types of sorption at interfaces). For interfaces with physical adsorption, variations in the diffusion activity differed in their smoothness with a notable rise for the contacts in the region of ~1000 K, and for Al/G/Al (with a double coating) in the region of ~1800 K, but with a different degree of nonmonotonicity. For the chemisorption interfaces formed during the hybridization of πz-dz orbitals, however, slow growth at the initial stages of heating in the high-temperature region (~2000 K) changed with an abrupt increase in both diffusion components. © 2016, Institute for Metals Superplasticity Problems of Russian Academy of Sciences. All rights reserved.


Gafner S.L.,Khakas State University | Gafner J.J.,Khakas State University | Zamulin I.S.,Khakas State University | Redel L.V.,Khakas State University
Journal of Computational and Theoretical Nanoscience | Year: 2012

The processes of melting and crystallization of Pt nanoclusters with a diameter ranging from 1.6 to 10 nm have been investigated using the molecular dynamics simulation. The performed simulation has shown that the melting begins with the surface of the cluster. Another feature of this phase transition is that it occurs in a temperature range where the liquid and solid phases can coexist. However, it is found that, for small platinum clusters, the melting and crystallization temperatures coincide with each other. The behavior of some thermodynamic characteristics of platinum nanoclusters is investigated in the vicinity of the solid-liquid phase transition. Analysis of the data obtained has revealed a number of regularities that are in agreement with the results of analytical calculations. In particular, the melting and crystallization temperatures of platinum nanoparticles are linear functions of N -1/3. However, the melting heat ΔH m and the melting entropy ΔS m vary in a more complex manner. © 2012 American Scientific Publishers All rights reserved.


Chepkasov I.V.,Khakas State University | Gafner Y.Y.,Khakas State University | Gafner S.L.,Khakas State University
Phase Transitions | Year: 2016

A series of computer experiments was conducted by the raw material evaporation and subsequent condensation to determine the most efficient regimes of copper nanoparticles synthesis. By variation of the cooling rate of the metal vapor the formation of Cu clusters were studied. The computer experiments showed the influence of different final temperatures on the shape of the resultant particles. This allowed to determine the conditions for a predominant formation of worm-like clusters of a spherical shape in the gas phase synthesis. © 2016 Informa UK Limited, trading as Taylor & Francis Group


Ageeva E.S.,Khakas State University | Shtygasheva O.V.,Khakas State University | Ryazantseva N.V.,Siberian State Medical University
Terapevticheskii Arkhiv | Year: 2011

Aim. To investigate association of polymorphisms of IL-1 genes and antagonist of IL-2 receptor (IL1Ra). Material and methods. Patients with chronic gastritis and ulcer were examined using the method of restriction analysis. Results. It was found that CCIL1beta and R4/R4IL1Ra are most prevalent allel variants in khakas population. Conclusion. It is expedient to define population risk and protective genotypes of development of ulcer associated with Helicobacter pylori in khakases. Helicobacter pylori.


Khakas State University | Entity website

12.07 ...


Khakas State University | Entity website

, 14.04 ...


Khakas State University | Entity website

12.07 ...


Khakas State University | Entity website

12.07 ...

Loading Khakas State University collaborators
Loading Khakas State University collaborators