ELASTIC INTERFACIAL WAVES IN DISCRETE AND CONTINUOUS MEDIA

Phonon spectra of bicrystals with relaxed grain-boundary structure dis play a variety of localized modes including long-wavelength acoustic m odes. Continuum solutions for localized waves that incorporate atomic- level elastic properties of the interface via discontinuity relations agree well with the latter modes. In contrast, classical solutions tha t depend only on bulk elastic properties do not. This demonstrates tha t the distinct atomic structure of the interface is a controlling fact or, and it is shown how local, atomic-level properties can be incorpor ated into continuum analyses of interfacial phenomena.