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Ust’-Abakan, Russia

Gafner S.L.,Khakassian State University | Redel L.V.,Khakassian State University | Gafner Yu.Ya.,Khakassian State University | Samsonov V.M.,Tver State University
Journal of Nanoparticle Research | Year: 2011

The heat capacity of copper and nickel clusters (from 2 to 6 nm in diameter) was investigated in the temperature range 200-800 K using molecular dynamics method and a modified tightbinding potential. The simulation results demonstrate a very good agreement with the available experimental data at T = 200 K and a fairy good agreement at higher temperatures. A number of regular trends are revealed in computer experiments which agree with the corresponding theoretical predictions. A conclusion is made that in the case of single free clusters the heat capacity may exceed the capacity of the corresponding bulk material. It is found that at 200 K, the copper nanocluster (D = 6 nm) heat capacity is higher by 10% and for nickel cluster by 13%. The difference diminishes with increasing the nanoparticles size proportionally to the relative number of surface atoms. A conclusion is made that very high values of the nanostructure heat capacity observed in laboratory experiments should not be attributed to free clusters, i.e., the effect in question is caused by other reasons. © 2011 Springer Science+Business Media B.V. Source


Gafner Y.Y.,Khakassian State University | Goloven'ko Z.V.,Khakassian State University | Gafner S.L.,Khakassian State University
Journal of Experimental and Theoretical Physics | Year: 2013

The structure formation in gold nanoparticles 1.6-5.0 nm in diameter is studied by molecular dynamics simulation using a tight-binding potential. The simulation shows that the initial fcc phase in small Au clusters transforms into other structural modifications as temperature changes. As the cluster size increases, the transition temperature shifts toward the melting temperature of the cluster. The effect of various crystallization conditions on the formation of the internal structure of gold nanoclusters is studied in terms of microcanonical and canonical ensembles. The stability boundaries of various crystalline isomers are analyzed. The obtained dependences are compared with the corresponding data obtained for copper and nickel nanoparticles. The structure formation during crystallization is found to be characterized by a clear effect of the particle size on the stability of a certain isomer modification. Nickel and copper clusters are shown to exhibit common features in the formation of their structural properties, whereas gold clusters demonstrate much more complex behavior. © Pleiades Publishing, Inc., 2013. Source


Samsonov V.M.,Tver State University | Kharechkin S.S.,Tver State University | Gafner S.L.,Khakassian State University | Redel L.V.,Khakassian State University | And 2 more authors.
Bulletin of the Russian Academy of Sciences: Physics | Year: 2010

Using two independent computer programs based on isothermal molecular dynamics method, we studied size effects during the melting and crystallization of Lennard-Jones nanoparticles and metallic clusters, the interaction in which was described by the cooperative potentials. We found that at nanoparticle radii exceeding a certain characteristic value, the melting point of nanoparticles is higher than their crystallization temperature. © Allerton Press, Inc., 2010. Source


Gafner Yu.Ya.,Khakassian State University | Gafner S.L.,Khakassian State University | Redel L.V.,Khakassian State University | Goloven'Ko Zh.V.,Khakassian State University
Journal of Nanoscience and Nanotechnology | Year: 2014

The opportunity of transition metals nanoclusters' usage as a data bits in memory devices for the recording transition "order-disorder" has been analyzed. Therefore, with the help of the molecular dynamics method on the basis of TB-SMA potential the simulation of metal nanoparticles (D = 1.6- 5.0 nm) crystallization processes have been studied. Influence of various conditions of crystallization on formation of internal structure in metal nanoclusters is investigated. The stability boundaries of various crystalline isomers are analyzed. The obtained dependences are compared with the corresponding data obtained for gold, copper and nickel nanoparticles having similar sizes. Nickel and copper clusters are shown to exhibit common features in the formation of their structural properties, whereas gold clusters demonstrate much more complex behavior. The limiting size of nanoparticles is determined, for which a structural "order-disorder" transition necessary for the data recording is still possible. Copyright © 2014 American Scientific Publishers All rights reserved. Source

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