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Structural transitions in melts as well as their dynamics are considered. It is supposed that liquid represents the solution of relatively stable solidlike locally favored structures in the surrounding of disordered normal-liquid structures. Within the framework of this approach the step changes of liquid Co viscosity are considered as liquid-liquid transitions. It is supposed that this sort of transition represents the cooperative medium-range bond ordering, and corresponds to the transition of the "Newtonian fluid" to the "structured fluid." It is shown that relaxation processes with oscillatinglike time behavior (omega approximately 10(-2) s(-1)) of viscosity are possibly close to this point.

Crystal growth and crystal coalescence processes in supercooled systems strongly depend on the concentration of crystallization centers. We perform atomistic dynamics simulations of the crystallization process in the ultrathin metallic film at different supercooling levels corresponding to supercooled liquid and amorphous solid states. Scaled relations are applied to identify the characteristic regimes in the time-dependent crystalline nuclei concentration: steady-state nucleation regime, saturation regime and coalescence regime. We show that the crystal growth at the saturation regime appears due to mixing nucleation and coalescence processes. We find that the crystallite coalescence realizes mainly through the mechanism of restructurization/absorption of crystal nuclei, whereas the mechanism of oriented attachment is manifested only at low levels of supercooling.

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