Interacting dipoles in type-I clathrates: Why glass-like though crystalline?T. Nakayama1 and E. Kanashita2
1 Materials Science Division, Argonne National Laboratory - 9700 South Cass Avenue, Argonne, IL 60439, USA
2 Advanced Photon Source, Argonne National laboratory - 9700 South Cass Avenue, Argonne, IL 60439, USA
received 25 October 2008; accepted in final form 19 November 2008; published December 2008
published online 3 December 2008
Almost identical thermal properties of type-I clathrate compounds to those of glasses follow naturally from the consideration that off-centered guest ions possess electric dipole moments. Local fields from neighbor dipoles create many potential minima in the configuration space. A theoretical analysis based on two-level tunneling states demonstrates that interacting dipoles are a key to quantitatively explain the glass-like behaviors of low-temperature thermal properties of type-I clathrate compounds with off-centered guest ions.
66.35.+a - Quantum tunneling of defects.
61.72.Bb - Theories and models of crystal defects.
61.43.-j - Disordered solids.
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