Unraveling the effect of isotropic strain on the transport properties of half-Heusler alloy LiScGe

Abstract

In the present work, we investigated the effect of isotropic strain, both tensile (up to 9%) and compressive (up to −9%) on the electronic structure and transport properties of LiScGe half-Heusler (hH) alloy. The electronic structure calculations using the density functional theory reveal that increase in tensile strain widens the energy band gap, whereas increase in compressive strain shortens it. The electronic thermal conductivity, κe= κ0-S2σT (where κ0 is the short-circuit electronic thermal conductivity) decreases under tensile strain whereas it increases under compressive strain with S2σT term playing a significant role in the determination of κe. The bipolar contribution to thermal conductivity (κbp) is found to decrease under tensile strain while it increases in case of compressive strain at strain values higher than − 3%. It is found that lattice thermal conductivity (κl) calculated using both the Slack′s equation and Callaway Model increases with increase in tensile strain in general whereas in case of compressive strain, κl decreases as strain is increased. Our results for transport properties show that increase in tensile strain leads to an overall increase in ZT values of n-type LiScGe and increase in compressive strain increases ZT of p-type LiScGe.