ON THE CONNECTION BETWEEN LOW-FREQUENCY VIBRATIONAL AND RELAXATIONAL MOTION IN GLASSES

In their low frequency inelastic scattering spectra, all glasses show a broad feature centered at similar to 1 THz, the so called Boson peak (BP). By now it has become clear that the BP is due to an increase in vibrational density of states (over the Debye value), due to localize d excitations. The organic glassformer meta-tricresylphosphate is pres ented as an example. A description in terms of strongly scattered phon ons is given as an illustration. A length scale for the spatial fluctu ations of elastic properties can be estimated from the BP. It is of th e order of 2 nm. Besides the vibrational excitation seen in the BP, re laxations are observed at still smaller frequencies, increasing in str ength as the glass is heated towards the glass transition temperature. Their strength rises with the fragility (in Angell's sense) of the gl ass and with its linear term in the low temperature specific heat, C-p . A simple picture is presented which connects relaxations with C-p (o r: the phonons of the BP with the two-level systems of C-p).