Secondary relaxation in the terahertz range in 2-adamantanone from theory and experiments

Article

关键词: CAGED MOLECULE-DYNAMICS;    BETA-RELAXATION;    SUPERCOOLED LIQUIDS;    GLASS-TRANSITION;    VISCOUS-LIQUIDS;   

DOI  :  10.1103/PhysRevB.101.104202

来源: SCIE

【 摘 要 】

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.

【 授权许可】

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