Interacting dipoles in type-I clathrates: Why glass-like though crystalline?

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: 19 November 2008

Abstract

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.