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arXiv · 1103.1441

Significance of Off-Center Rattling for Emerging Low-lying THz Modes in type-I Clathrates

Tsuneyoshi Nakayama·Eiji Kaneshita
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Abstract

We show that the distinct differences of low-lying THz-frequency dynamics between type-I clathrates with on-center and off-center guest ions naturally follow from a theoretical model taking into account essential features of the dynamics of rattling guest ions. Our model analysis demonstrates the drastic change from the conventional dynamics shown by on-center systems to the peculiar dynamics of off-center systems in a unified manner. We claim that glass-like plateau thermal conductivities observed for off-center systems stem from the flattening of acoustic phonon dispersion in the regime |k|<|G|/4. The mechanism is applicable to other systems such as glasses or relaxers.

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Tsuneyoshi Nakayama, Eiji Kaneshita. 2011-09-27. Significance of Off-Center Rattling for Emerging Low-lying THz Modes in type-I Clathrates. https://doi.org/10.1143/jpsj.80.104604

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