Atomistics of pre-nucleation layering of liquid metals at the interface with poor nucleants

SD Ma and AJ Brown and R Yan and RL Davidchack and PB Howes and C Nicklin and QJ Zhai and T Jing and HB Dong, COMMUNICATIONS CHEMISTRY, 2, 1 (2019).

DOI: 10.1038/s42004-018-0104-1

Liquid layering at heterogeneous solid/liquid interfaces is a general phenomenon, which provides structural templates for nucleation of crystalline phases on potent nucleants. However, its efficacy near poor nucleants is incompletely understood. Here we use a combination of X-ray crystal truncation rod analysis and ab initio molecular dynamics to probe the pre-nucleation liquid layering at the sapphire-aluminium solid/liquid interface. At the sapphire side, a similar to 1.6 aluminium-terminated structure develops, and at the liquid side, two pre-nucleation layers emerge at 950 K. No more pre-nucleation layer forms with decreasing temperature indicating that nucleation of crystalline aluminium through layer-by-layer atomic adsorption of liquid atoms is not favoured. Instead, the appearance of stochastically-formed nuclei near the substrate is supported by our experiments. Nucleation on poor nucleants is dominated by the stochastic nucleation events which are substantially influenced by the pre-nucleation layers that determine the surface structure in contact with the nuclei.

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