Atomic-scale insights into structural and thermodynamic stability of spherical Al@Ni and Ni@Al core–shell nanoparticles

Atomic-scale comprehension of structure and thermodynamic stability of metallic core–shell nanoparticles is important for viewpoints of both their synthesis and applications. Thermodynamic and structural properties of Al@Ni and Ni@Al core–shell nanoparticles are investigated at various temperatures by using molecular dynamics (MD) simulations within the interactions defined by the many-body embedded atom model (EAM). The sizes of Al@Ni core–shell nanoparticles and their pure counterparts are chosen as two different values of about 5 nm and 10 nm in this study. MD method is used to calculate the total energy, one-body particle density, radial distribution function, and heat capacity to estimate the melting temperatures of the core–shell systems considered in the present study. Our estimated melting temperatures of core–shell nanoparticles are also verified by doing common neighbor analysis (CNA). MD study shows that a distinct two-stage melting takes place during the heating of the Al@Ni core–shell nanoparticles, although their melting mechanism has started from surface into interior. It is reported that the width of the melting temperature of the core–shell nanoparticles is dependent not only on the bulk melting points of their pure metals but also on the ratio of the shell thickness and the core size of the nanoparticles.