Bezpalchuk V. Multiscale simulation of phase formation in binary nanosystems with FCC structure

The thesis treats the development of multiscale computer models for deposition, diffusion interaction, ordering of nanofilms and their application to technologically important Ni-Al and Fe-Pt systems. The object of the study in nanoscalefilms inmulti-layerfoils for SHS reactions and nanoscale bimetallicfilms for magnetic recording of information. Methods of research: the classical method of molecular dynamics, the original and specially developed stochastic kinetic mean field method, the kinetic method of Monte Carlo. New results: 1. Phase formation in the Ni-Al thin-film system during annealing process of deposited films is determined by: a) substrate temperature during deposition, b) deposition sequence, c) orientation of the substrate. In particular, the cold deposition of Ni on Al substrate with further annealing process leads to the formation of the disordered (probably liquid) solution as the first stage reaction diffusion. Deposition on a hot substrate leads to the formation of ordered phase further becomes a barrier. 2. KMF method and its modification SKMF first applied to the vacancy diffusion mechanism with the steady-state approximation of the vacancy subsystem, which allows to significantly increase the time step of the calculation of the kinetics of diffusion processes. 3. Adding noise frequencies in the mean-field kinetic equations allow correctly simulate the first-order phase transitions in alloys. Considering noise allow the possibility to predict and describe these new phenomena: a) "Quantum" coalescence in the 1D structure at the final stage of spinodal decomposition in nanorod. b) Propagation of the front of the reorientation of the L10 structure from a free surface to the center of the sample. c)The presence of noise threshold below which decomposition with ordering in finite sample not happens. Within the application of the method to the simulation of the decomposition with ordering in supersaturated alloy with concentration 7/8. That was made possible by the adding of noise in the simulation. 4. Reducing the size of the nanoparticles significantly reduces the value of the local order parameter in the area of ordering. 5. SKMF method used for the first time for simultaneous determination of the tracer diffusion kinetics and ordering structures such as L12 and L10. In this modified method based on the obtained tracer concentration profiles diffusion coefficients for a range of temperatures were found. Also, it was introduced a local long-range order parameter. The practical significance of the results is the fact that the obtained model of the effect of substrate temperature and its orientation to the reactivity of multilayer can optimize the technology of manufacturing the nanolayer foils for further applications at SHS reactions. Predicted in the work process of the reorientation in the surface layers of the L10 structure can be a determining factor in the technology of magnetic recording media. Developed SKMF simplified method can be widely used in many numerical models of the reaction and phase transformation.