Size and temperature effects on surface energy of Au and Fe nanoparticles from atomistic simulations

In the aim to improve our atomistic understanding of the structural properties and energetic properties of metallic nanoparticles (around similar to 180 to 6000 atoms), molecular dynamics (MD) is employed to study properties of gold nanoparticles (AuNPs) and iron nanoparticles (FeNPs). We used the radial distribution function (RDF) to determine the structural evolution with temperature, and used atomic coordination numbers to define the different low-index facets. We found that generally for AuNPs the (111) facet showed the lowest surface energy compared to (100) and (110) facets. In contrast, FeNPs exhibited a higher stability for the (110) facet. Furthermore, based on surface energy criterion, FeNP392 and FeNP4314 showed morphologies consistent with decahedron and truncated-octahedron, respectively. The equilibrium crystal shape of AuNPs and FeNPs are found using the Atomic Simulation Environments (ASE) freeware to create the well-known morphologies and using their surface energy to compare it with ours.