DISORDER EFFECTS ON GLASSY DYNAMICS - SEPARATION OF ORIENTATIONAL ANDPOSITIONAL CORRELATIONS

The pressure dependence of the spectral distributions of the glass (i. e. amorphous). orientational glass (OG) and stable (monoclinic) crysta l phases of ethanol is investigated by means of neutron inelastic scat tering under the same thermodynamic conditions. Parameters characteriz ing the anharmonic behavior are derived from the measurements and show that the orientationally disordered crystals follow a behavior closer to the true glass than to the ordered crystals. Such a similarity mak es the orientationally disordered crystals ideal candidates for quanti tative studies of the glass transition on a model system where the mic roscopic dynamics can be accounted in full. (C) 1998 Elsevier Science B.V. All rights reserved.