Influence of lattice mismatch of nano-holed substrate on the crystallization of Lennard-Jones liquids

Crystallization often occurs on the substrate and is influenced by the morphology of the surface. This study investigates the process of crystallization in Lennard-Jones liquids on lattice-mismatched substrates with a cylindrical hole, utilizing molecular dynamics simulation. By decreasing the value of δ, representing the difference in lattice constant between the substrate and the bulk crystal, various crystallization behaviors are observed and studied. More precisely, as δ drops progressively, the crystallization can be shown to have three distinct stages: I at $-0.03<\delta \le 0$, nucleation takes place inside the hole, and the crystalline nucleus then grows and spreads throughout the entire substrate, resulting in crystals dominated by the fcc structure; II at $-0.09<\delta \le -0.03$, nucleation occurs both inside and outside the hole, leading to the formation of a random hcp&fcc structure; III at $-0.15\le \delta \le -0.09$, nucleation begins outside the hole with random hcp&fcc planes parallel to the surface of the substrate and then extends into the hole. The atoms in the crystalline layer directly above the pores are more ordered compared to the surrounding regions. Inside the cavities is a liquid layer about two particles thick, forming between the substrate and the resulting crystal to reduce the interfacial energy due to a significant mismatch. The results of our study demonstrate that using a substrate with a mismatched lattice and a nanoscale hole can lead to different crystallization processes and the formation of varied forms. This finding contributes to our understanding of crystallization and offers an atomic-level approach to designing the structure of crystals.