Atomistic explanation of failure mechanisms of thermoelectric type-VIII clathrate Ba8Ga16Sn30

Abstract

The type-VIII clathrate Ba8Ga16Sn30 (BGS) is a promising thermoelectric material with a cage-guest structure. The failure mechanisms behind the tetrahedrally bonded framework, which are vital for understanding the structure - mechanical property relationship, are still unrevealed. Here we conduct DFT calculations to investigate the intrinsic mechanical behavior of BGS. BGS has the ideal strength of 2.65 GPa under (100)/[010] shearing. The fast stretching and breakage of Sn-Sn bond give rise to the sudden failure of Ga-Sn bond, resulting in the collapse of void space and the structural damage. Under [100] tension, the structural failure is due to the breakage of Ga-Sn bonds that are nearly parallel to the tensile direction. Besides, Ga-Sn bonds are dominant for maintaining the local rigidity since they contribute the vast majority of structural resistance.