Structure-dependent vibrational properties of metallic nanoclusters

The thermally vibrational properties of icosahedral (ICH) and face-center-cubic (FCC) copper nanoclusters has been compared by carrying out molecular dynamics simulations with a local-environment-dependent tight-binding potential. Although, both ICH and FCC copper nanoclusters exhibit a low- and high-energy enhancement of vibrational density of states (VDOS) in comparison with the bulk copper, the vibrational properties of nanoclusters show a strong structure-dependent feature. The different structure is revealed to result in the different atom package, the different lattice shrinkage, the different local pressure, and thus, the different VDOS. The different atom package at the surfaces of clusters is responsible for the different low-energy VDOS in a different power-law behavior between the FCC and ICH clusters. The lattice contraction and the internal pressure in the sense of the bulk are unified, to explain the enhanced high-energy tail in the VDOS of FCC clusters, but not in the case of ICH clusters.