  The phonon scattering processes on the three solid phases of ethanol are
investigated by means of thermal conductivity, light and neutron scattering
measurements as well as molecular dynamics simulations on single-crystalline
models for the two crystalline modifications (fully ordered monooclinic and
orientationally disordered bcc phases). The orientationally disordered crystal
is found to exhibit a temperature dependence of the thermal conductivity that
is remarkably close to that found for the structurally amorphous solid,
specially at low temperatures. The results, together with measurements of the
Brillouin linewidths as derived from light scattering measurements emphasize
the role of orientational disorder on phonon scattering. The experimental
results obtained on polycrystal samples are then discussed with the aid of
computer simulations on single-crystalline models of both bcc and monoclinic
crystals. Our findings are in good agreement with the wealth of thermodynamic
and dynamic data vailable so far [1], but are in stark contrast with inferences
made from the analysis of inelastic X-ray data on polycrystalline samples [2],
where a common nature for the excitations in all phases is postulated.
