High-frequency vibrational properties of metallic nanocrystalline grain boundaries.

The high-frequency phonon properties of a computer generated nanocrystalline (nc) fcc Ni with a mean grain size of 5 nm are investigated by directly calculating the on-site phonon Green's function using a recursion technique based on a continued fraction representation. It is found that the high-frequency tail, observed in both experiment and previous simulation work, arises primarily from spatially confined vibrational modes forming within the nc grain boundary regions.