Our calculated vibrational properties of Ag nanocrystals show three novel, size dependent features which have broad implications for their thermodynamic properties and stability. There is an enhancement in the vibrational density of states at low frequencies and an overall shift of the high frequency band beyond the top of the bulk phonons. Additionally, the vibrational projected density of states of the surface atoms scales linearly with frequency, at low frequencies. The generality of these results for systems with bond-order–bond-length correlation, low average coordination, and large ratio of surface to bulk atoms helps explain qualitatively several recent experimental observations.

• Received 23 March 1998

DOI:https://doi.org/10.1103/PhysRevLett.81.1453