Remarkable nuances of crystallization: From ordinary crystal nucleation to rival mechanisms of crystallite coalescence

TL;DR

This study uses atomistic simulations to explore how supercooling levels influence crystal nucleation and coalescence mechanisms in ultrathin metallic films, revealing distinct regimes and coalescence pathways.

Contribution

It provides detailed insights into the regimes of crystallization and identifies the dominant mechanisms of crystallite coalescence at different supercooling levels.

Findings

Crystallization regimes include steady-state nucleation, saturation, and coalescence.

Coalescence mainly occurs via restructurization/absorption of nuclei.

Oriented attachment occurs only at low supercooling levels.

Abstract

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.