Search

Using first-principles calculations,we investigated the thermoelectricproperties of a newly synthesized Si-based ternary clathrate K8Al8Si38, composed of ∼1 nm hollowcages with a metal atom inside. This compound contains solely Earthabundant elements. We found that, similar to other nanostructuredtype I clathrates, this system is a semiconductor and has a low thermalconductivity (∼1 W/mK). It was long believed that the merepresence of rattling centers was responsible for the low lattice thermalconductivity of type I clathrates. We found instead that the cagestructural disorder induced by atomic substitution plays a crucialrole in determining the conductivity of these materials, in additionto the dynamics of the guest atoms. Our calculations showed that thelatter is substantially affected by the charge transfer between themetal and the cages. Our results provide design rules for the searchof new types of promising nanocage structured thermoelectric materials. [ABSTRACT FROM AUTHOR]