Lattice induced crystallization of nanodroplets: the role of finite-size effects and substrate properties in controlling polymorphism

TL;DR

This study uses molecular dynamics simulations to explore how substrate properties and finite-size effects influence the crystallization and polymorphism of nanodroplets, revealing mechanisms for controlling nanoparticle crystal structures.

Contribution

It demonstrates that substrate lattice parameters can be tuned to selectively induce different crystal polymorphs in nanodroplets, highlighting the role of cross-nucleation pathways.

Findings

Different crystal structures can be achieved by tuning substrate lattice parameters.

Hexagonal and body-centered cubic polymorphs can grow on face-centered cubic substrates.

Large BCC clusters facilitate the growth of HCP polymorphs through cross-nucleation.

Abstract

Targeting specific technological applications requires the control of nanoparticle properties, especially the crystalline polymorph. Freezing a nanodroplet deposited on a solid substrate leads to the formation of crystalline structures. We study the inherent mechanisms underlying this general phenomenon by means of molecular dynamics simulations. Our work shows that different crystal structures can be selected by finely tuning the solid substrate lattice parameter. Indeed, while for our system, face-centered cubic is usually the most preponderant structure, the growth of two distinct polymorphs, hexagonal centered packing and body-centered cubic, was also observed even when the solid substrate was face-centered cubic. Finally, we also demonstrated that the growth of hexagonal centered packing is conditioned by the appearance of large enough body-centered cubic clusters thus suggesting the presence of a cross-nucleation pathway. Our results provide insights into the impact of nanoscale effects and solid substrate properties towards the growth of polymorphic nanomaterials.