We applied the recently developed Generalized Langevin equation (GLE) approach for dielectric response of liquids and glasses to link the vibrational density of states (VDOS) to the dielectric response of a model orientational glass. The dielectric functions calculated based on the GLE, with VDOS obtained in experiments and simulations as input, are compared with experimental data for the paradigmatic case of 2-adamantanone at various temperatures. The memory function is related to the integral of the VDOS times a spectral coupling function gamma(omega(p)), which tells the degree of dynamical coupling between molecular degrees of freedom at different eigenfrequencies. With respect to previous empirical fittings, the GLE-based fitting reveals a broader temperature range over which the secondary relaxation is active. Furthermore, the theoretical analysis provides clear evidence of secondary relaxation being localized within the THz (0.5 - 1 THz) range of eigenfrequencies, and thus not too far from the low-energy modes involved in a relaxation. In the same THz region, the same material displays a crowding of low-energy optical modes that may be related to the secondary relaxation.
Secondary relaxation in the terahertz range in 2-adamantanone from theory and experiments / B. Cui, J.F. Gebbia, M. Romanini, S. Rudić, R. Fernandez-Perea, F.J. Bermejo, J. Tamarit, A. Zaccone. - In: PHYSICAL REVIEW. B. - ISSN 2469-9950. - 101:10(2020 Mar 20).
|Titolo:||Secondary relaxation in the terahertz range in 2-adamantanone from theory and experiments|
ZACCONE, ALESSIO (Ultimo)
|Settore Scientifico Disciplinare:||Settore FIS/03 - Fisica della Materia|
Settore FIS/02 - Fisica Teorica, Modelli e Metodi Matematici
|Data di pubblicazione:||20-mar-2020|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.1103/PhysRevB.101.104202|
|Appare nelle tipologie:||01 - Articolo su periodico|