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Atomistichesky modelling

Thus, mechanisms of phase changes in nanochastitsah demand further more detailed analysis. According to item 1.1, theoretical representations in this area are limited basically to phenomenological level, but thus there is a number of open questions.

As marked in the beginning of 80th JU.I.Petrov [33], the statistical physics predicts the expressed phase changes only in very big systems, and the statistical theory of phase changes in small objects is not developed till now. Experimental data on fusion nanochastits are poor enough, are characterised by a wide scatter, and their reliability raises some doubts. As to works on crystallisation nanokapel they are individual. With the account of it, the special urgency is got by application atomisticheskogo modelling for the further research structural transfomations in nanochastitsah.

The COMPUTER wide circulation in 70th has led to the beginning of researches in this area. The review of the early works concerning in basic to very small nanoklasteram is presented to monographies [33], containing from several atoms to 100 atoms. It is necessary to notice also, that the Monte-Carlo technique (MK) which almost all researchers in favour of a method of molecular dynamics (MD) subsequently have refused, answering to modelling in a real time mode originally was more often applied. As an exception it is possible to note master's thesis D.N. The Sokolov [34], executed under the guidance of N.J.Sdobnjakova, and also corresponding publications of the specified authors [35, 36]. Both in our works, and in works of other authors connected with application of method MD, phase change was found out on a break (or to inclination change) on kaloricheskoj by the curve, i.e. on dependence potential (cohesive) making and specific (counting on one atom) intrinsic energy. Method MK also predicts a hysteresis of fusion-crystallisation and presence of crosspoint of corresponding curves. However we believe, that method MK yields the overestimated values of melting points and crystallisations. Melting point Tmмы we register at first jump displays (derivative tearing up) from the specified size or we find as average value of temperatures of the beginning and fusion end. As a whole, such approaches are represented quite reasonable and will be co-ordinated with definition of phase change of the first sort. Really, to phase changes of the first sort carry the transferrings accompanied by jumps first derivative of the chemical potential (or energy of Gibbs). Jumps of these derivatives answer presence of heat effect and volume jump. In an assumption, that the volume of system "particle-steam" does not vary at phase change, heat of cooling will be equal to intrinsic energy respective alteration. Further, if it is used isothermal MD or method MK (the Metropolis schema),

It is possible to set slow rise in temperature up to temperature, 25

Obviously exceeding macroscopical melting point. Then the quantity of warmth spent for fusion of a particle, will low fidelity equally to jump of a potential part of intrinsic energy.

It is necessary to notice, that, according to [33], fusion klasterov was found out even with reference to the particles containing only 7 atoms. Differently, at N

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A source: Talyzin Igor Vladimirovich. MOLECULAR DYNAMIC INVESTIGATION OF THERMODYNAMIC AND KINETIC ASPECTS OF MELTING AND CRYSTALLIZATION OF METAL NANOPARTICLES. DISSERTATION on competition of a scientific degree of the candidate of physical and mathematical sciences. Tver - 2019. 2019

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