Band structure and thermoelectric properties of type-III barium clathrates

The electronic structure of type-III Ba clathrates was calculated by using a full-potential linearized augmented plane-wave (FLAPW) method. In the calculation of Ba
₆
Al
₄
Si
₂₁
a virtual crystal approximation was used. The calculated band structure shows that Ba
₆
Al
₄
Si
₂₁
is an intrinsic semiconductor with an indirect gap. The top of the valence band is at the Gamma point and the bottom of the conduction band is on the Lambda axis. The thermoelectric properties are calculated by using the calculated electronic states