  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.
