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 (DFT). 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 cIcosahedron ( 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 n c 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).