Size-dependent surface energy of Ar and Si nanovoids

A simple model for the size dependence of liquid-vapor surface energy of a liquid drop, free of any adjustable parameter, has been extended for the size dependence of the surface energy of nanovoids in this work. Considering nanovoids, there is a negative curvature on the void surface, which is completely different from nanoparticles or liquid drops, which have positive curvature surfaces. Thus curvature has an important effect on material properties. Moreover, by introducing negative curvature into the model for deduction of liquid-vapor surface energy, a successful prediction for the behaviour of argon (Ar) and silicon (Si) surface energy on the surface of nanovoids are obtained, which further confirms the role of curvature. Furthermore, it is shown that the surface energy of nanovoids increases as void size is reduced, suggesting a greater difference in energy between surface atoms and interior atoms, especially when void size is smaller than 4 nm. This is owing to the fact that the surface energy gradually approaches that of the bulk when the void size is larger than 4 nm. Thus, the effect of size on the surface energy of voids is significant when the voids are of small dimensions.