Size and Structural Dependence of Cohesive Energy in Cu

The cohesive energy of Cu clusters (E-c) containing different numbers of atoms (n) in the metastable structures of pyramids, nanotubes, nanorods, films, and icosahedrons is determined using ab initio density functional theory (DFF). Modeling of E-c(n) functions is also implemented and discussed. Both theoretical and simulation results show that E-c(n) is a function of the surface bond deficit, and E-c(n) increases monotonically as n decreases, as follows: E-cNanotube(n) > E-cPyramid(n) > E-clcosahedron(n) > E-cNanorod(n) > E-cFilm(n) for a given n. This observed continuity of the E-c(n) functions implies that the quantum effect of E-c(n < n(c)) is not influenced by n or a size effect but instead by a structural effect, where nc denotes a critical value of n when the bulk crystalline structure is no longer stable for n < n(c). This suggestion is in good agreement with the results obtained from the observed distributions of the density of states (DOS).