Struttura della materia
Theory of anomalous vibrational properties of disordered solids
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Europe/Rome
Aula 7 (Edificio E.Fermi)
Aula 7
Edificio E.Fermi
Description
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.