Equivalent surface energy of nanovoids in metallic crystals

Abstract

Nanovoids and helium nanobubbles are formed in ion irradiated metals. Due to the surface effect, these nanostructures are in a polyhedron shape. However, a smooth surface is generally used in the classical theoretical model. In this work, we performed molecular static/dynamic simulations to assess the elastic field around nanovoids in six metals, W, Fe, V, Ni, Cu and Al. Compared to theoretical model, a new equivalent coefficient for the surface energy is proposed to bridge the gap between the molecular simulation and the theoretical prediction, while a size effect in Ni, Cu and Al crystals as the diameter is less than 5 nm. Most importantly, whether the size effect exists, their equivalent surface energies are different from their average surface energies of previous crystals. The proposed concept of equivalent surface energy may provide a convenient way to overall evaluate the surface effect of nanovoid in metallic crystals.