Electronic structure and thermoelectric properties of clathrate compounds Ba8Al16Si30 and Ba8Al16Ge30

Electronic structure of Group IV-based Clathrate Compounds substituted by Al, i.e., Ba8Al16Si30 and Ba8Al16Ge30, is calculated by the first principle method, i.e., the Full-potential Linearlized Augmented Plane Wave (FLAPW) method, based on the density functional theory. The calculated results show that these compounds are indirect semiconductors with the band gap 0.39 eV (Ba8Al16Si30) and 0.41 eV (Ba8Al16Ge30). Using the calculated electronic structure, thermoelectric properties such as Seebeck coefficient, electrical conductivity, electronic thermal conductivity and the figure of merit ZT are calculated by using the constant relaxation time approximation. The calculated result reproduces the experiment reasonably well.