Theory of anomalous vibrational properties of disordered solids

by Prof. Walter Schirmacher (Phys. Dept., Technische Universität München)

Friday 19 Sept 2008, 15:00 → 17:00 Europe/Rome

Aula 7 (Edificio E.Fermi)

The vibrational properties of disordered solids differ very much from their crystalline counterparts. In the low-frequency regime, where crystals exhibit the Debye law in the density of states (DOS) disordered solids exhibit a strong enhancement of the DOS as compared to the Debye prediction. A theory is presented based on a model in which local elastic constants fluctuate in space. This model is solved in mean-field approximation. The enhancement of the DOS is shown to be due to the appearance of a disorder-induced band of irregular vibrational states. Explicit expressions for the inelastic light- neutron- and X-ray scattering cross-sections are presented and shown to compare well with experiments and results of simulations.