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).
Secondary relaxation in the terahertz range in 2-adamantanone from theory and experiments
A. ZacconeUltimo
2020
Abstract
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.File | Dimensione | Formato | |
---|---|---|---|
BK13564_revised.pdf
accesso aperto
Tipologia:
Post-print, accepted manuscript ecc. (versione accettata dall'editore)
Dimensione
1.35 MB
Formato
Adobe PDF
|
1.35 MB | Adobe PDF | Visualizza/Apri |
PhysRevB.101.104202.pdf
accesso aperto
Tipologia:
Publisher's version/PDF
Dimensione
1.55 MB
Formato
Adobe PDF
|
1.55 MB | Adobe PDF | Visualizza/Apri |
Pubblicazioni consigliate
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.