Electronic Structure of I-M8Ga16Sn30 (M = Ba, Sr, Yb) by First-Principles Calculation

Abstract

Sn-based clathrates possess excellent thermoelectric properties ascribed to their higher Seebeck coefficient and lower thermal conductivity. Guest atoms significantly modulate the thermoelectric properties of Sn-based calculates because of their diverse atomic radius and interactions with framework atoms. Thus, we explored the electronic structure of I-M 8 Ga 16 Sn 30 (M = Ba, Sr, Yb) by first-principles calculation. Results revealed significant differences between Yb 8 Ga 16 Sn 30 and M 8 Ga 16 Sn 30 (M = Ba, Sr,). In particular, the Yb-filled compound substitution possesses lowest formation energy and the off-center distance of the Yb atom is the largest compared with the other structures. I-M 8 Ga 16 Sn 30 (M = Ba, Sr, Yb) is an indirect band gap semiconductor, and the enhanced hybridization effect between the guest and framework atoms' orbits exists because the Yb f orbit results in a decrease in band gap. Ba-and Srfilled clathrates have similar valence bands but slightly different conduction bands; however, Yb 8 Ga 16 Sn 30 possess the spiculate density of states near the Fermi level that reveals excellent thermoelectric properties.