On the reaction coordinate for seeded crystallisation

TL;DR

This study uses computer simulations to investigate how small crystalline seeds influence the nucleation process in undercooled Lennard-Jones liquids, highlighting the importance of seed structure and reaction coordinate definition.

Contribution

It demonstrates the differential impact of BCC and FCC seeds on crystallisation rates and emphasizes the role of structural information in reaction coordinate selection.

Findings

BCC seeds enhance crystallisation more than FCC seeds

Largest crystalline cluster size shows memory effects influenced by seed structure

Structural details are crucial for defining effective reaction coordinates

Abstract

Small pre-structured seeds introduced into an undercooled fluid are known to increase the crystal nucleation rate by some orders of magnitude, if the structure of the seeds is commensurate with the bulk crystalline phase. The presence of such seeds also alters the crystallisation mechanism by favouring particular structures at the early stages of the nucleation process. Here, we study with computer simulations the effect of small face-centred cubic and body-centred cubic seeds on the crystallisation of a Lennard-Jones liquid in the strongly undercooled regime. We find that seeds with body-centred cubic structure lead to a larger enhancement of the crystallisation rate than face-centred cubic seeds. An analysis of recurrence times reveals that the size of the largest crystalline cluster used as reaction coordinate is affected by pronounced memory effects, which depend on the particular seed structure and point to the importance of structural information in the definition of a good reaction coordinate for crystallisation.