Calculating the Size-dependent Surface Energy of Metallic Spherical Nanoparticles and Nanocavities Using Molecular Dynamics

The unique characteristics of nanostructures are mainly due to their large surface to volume ratio. One of the most important quantities in investigating the surface properties of materials is the surface energy. Therefore, calculating the surface energy is necessary for the proper understanding of the behavior and properties of nanostructured materials. The present study investigates the size-dependent surface energy of crystalline nanoparticles and nanocavities of aluminum, silver, copper, and iron. For this purpose, spherical nanoparticles and nanocavities with different radiuses are modeled by molecular dynamics simulations and their surface energy is obtained. The simulation results demonstrate that for nanoparticles and nanocavities with sufficiently small radiuses in the range of a few nanometers, the surface energy depends on the size of the nanostructure. For spherical nanoparticles, the surface energy increases with increasing nanoparticle radius, while for the spherical nanocavities, the surface energy decreases by increasing nanocavity radius. Also, the surface energy variation with size is more intense for nanocavities in comparison with nanoparticles. By increasing the radius, the surface energy of nanoparticles and nanocavities approaches to an asymptotical value, which is the surface energy of a crystalline flat surface or the Gibbs surface energy for the crystallographic surface orientation with the maximum surface energy.