Capillary pressure and phonons in Ag, Au, Cu and Ni nanoparticles

Spherical nanciparticles of fcc metals with diameters between 2 and 10 nm have been studied by molecular-dynamics simulations. The results show that despite of the small size of the clusters the, Kelvin-equation accounts for the capillary pressure building up in the particles. Furthermore, the simulations show that the capillary pressure leads to a shift of the local vibrational density of states in the core of the particles to higher energies. The cluster's total vibrational density of states is found to be broadened by the contributions from surface atoms. The connection between this broadening and the density of states in nanocrystalline materials is discussed.