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Dynamic Nanostructuring of Crystalline Materials at Premelting Stage


A.N. Shebanov, E.V. Bogatikov, L.A. Bityutskaya, E.N. Bormontov

In order to study collective processes in the dynamics of crystalline lattice with the use of molecular dynamics method a simulation of atomic vibrations was made in two-dimensional triangle lattice of argon. The calculations were performed within the temperature range of 0.2Tmelt up to Tmelt. Lenard-Jones potential was used as a potential of interatomic interaction. To prevent distortions of simulation of the collective processes in the crystal lattice dynamics algorithm of computation was applied that did not include renormalization velocity of travel for the atoms. Using methods of non-linear dynamics formation of the areas of cooperative motion was found for a large temperature interval. The lifetime of the areas with cooperative motion at T~0.95Tmelt was found to be of ~ 100 ps (for the time of simulation after getting of thermodynamic equilibrium equal to 650 ps). While approaching to the melting temperature the size of the areas of cooperative motion became comparable with the size of simulation area (for the size of simulated crystal lattice from 50×50 to 200×200 atoms). Analysis of behaviour of kinetic and potential energy of the atoms with different level of participation in the cooperative motion has demonstrated that formation of the areas of cooperative motion results in a decrease of potential energy for the atoms participating in cooperative motion and transition of this energy to the kinetic energy of adjacent atoms that do not participate in the cooperative motion. As a result the regions of local heating appear inside the crystal and while approaching the temperature of ~ 0.9Tmelt the areas of local melting are formed. The obtained results are considered as a mechanism of heterophase melting proposed by Ya.Frenkel as a phenomenological model. Results of molecular-dynamic simulation are in a good agreement with a number of experimental works where heterophase melting was observed for thin metal films. On the one hand, formation of heterophase fluctuations in a wide temperature range puts forward such problems as temperature instability of metallization in VLSI, inhomogeneity of nanoscale doping caused by segregation processes at the boundaries of heterophase fluctuations. On the other hand, there appears a prospect for elaboration of the new ways for formation of the nanostructured surfaces and methods of doping.

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