Interacting Dipoles in Type-I Clathrates: Why Glass-like though Crystal?

TL;DR

This paper explains why certain crystalline clathrates exhibit glass-like thermal properties at low temperatures by modeling off-centered guest ions as interacting electric dipoles, revealing the importance of dipole interactions and predicting a glass transition.

Contribution

It introduces a theoretical model of interacting dipoles in type-I clathrates to explain their glass-like thermal behavior and predicts a glass transition.

Findings

Interacting dipoles create multiple potential minima.

The model quantitatively explains glass-like thermal properties.

A predicted glass transition in type-I clathrates.

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.From this analysis, we predict the existence of a glass transition.