The vibrational density of states (VDOS) of nanoclusters and nanocrystallinematerials are derived from molecular-dynamics simulations using empiricaltight-binding potentials. The results show that the VDOS inside nanoclusterscan be understood as that of the corresponding bulk system compressed by thecapillary pressure. At the surface of the nanoparticles the VDOS exhibits astrong enhancement at low energies and shows structures similar to that foundnear flat crystalline surfaces. For the nanocrystalline materials an increasedVDOS is found at high and low phonon energies, in agreement with experimentalfindings. The individual VDOS contributions from the grain centers, grainboundaries, and internal surfaces show that, in the nanocrystalline materials,the VDOS enhancements are mainly caused by the grain-boundary contributions andthat surface atoms play only a minor role. Although capillary pressures arealso present inside the grains of nanocrystalline materials, their effect onthe VDOS is different than in the cluster case which is probably due to theinter-grain coupling of the modes via the grain-boundaries.
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