Using dangling bond density to characterize the surface energy of nanomaterials

Taking f.c.c Ag, Al, Au, Ir, Pd, Pt, Rh and b.c.c Cr, Fe, Mo, Nb, Ta, V, W as examples, the energetic and bonding features of unrelaxed cubic nanoparticles were investigated by the modified embedded atom method. The surface free energy increases almost inversely with the decreasing feature sizes. This is the essential reason for the fantastic microstructures and distinct properties observed at the nanometer scale. According to the analysis on atomic bonding states, we further found that the size-dependent surface energy is directly associated with the dangling bond density. Summing up these two aspects, the dangling bond density, a microscopic parameter, is believed to be one of the intrinsic physical quantities characterizing the structures and properties of nanomaterials.