Dielectric Screening and Phonon-Dispersion in Metallic Glasses

Expressions for the phonon frequencies of the binary and ternary metallic glasses are derived on the basis of various dielectric screenings. A model which assumes a central force, effective between nearest neighbours, and a volume dependent force is adopted. The phonon frequencies of longitudinal and transverse phonons for the binary metallic glasses Ca70Mg30, Mg70Zn30, and Cu57Zr43 and for the ternary metallic glass Pd77.5Si16.5Cu6 are computed. The theoretical results compared with experimental data underline the importance of dielectric screening by conduction electrons.