Soft and hard shells in metallic nanocrystals - art. no. 193412

The inhomogeneous elastic properties of metallic nanocrystals are studied u sing semiempirical potentials for Au. Pb, Ag, and Cu. The enhanced low- and high-frequency modes are found to be spatially localized in two shells, a soft surface shell and a hard transition shell. Our analysis shows that the linear frequency dependence of the vibrational density of states is attrib uted to the two-dimensional nature of the surface shell that is independent of the system size, while the high-frequency tail mainly comes from the tr ansition shell.