Study of the Zn occupancy leading to the stability improvement for Cu6Sn5 using a first-principles approach

The influences of Zn doping on the relative stability of hexagonal and monoclinic Cu6Sn5 were investigated using a first-principles approach. It was found that the phase stability of monoclinic and hexagonal Cu6Sn5 could both be improved by Zn doping. For the monoclinic structure, Zn atoms preferentially occupied the 4e (Sn3) sites, it was 2c (Sn1c) sites for the hexagonal Cu6Sn5. The results of density of states demonstrated that hybridization of Zn-d and Sn-s state was the dominant factor for the stability improvement for both structures. Moreover, the Zn atoms concentration corresponding to the most stable structure for hexagonal Cu6(Sn,Zn)5 was 7.54%, which was consistent with the experimental results.

► Zn atoms preferentially occupied the 4e(Sn3) sites in the monoclinic Cu6Sn5.
► Zn atoms preferentially occupied the 2c(Sn1c) sites in the hexagonal Cu6Sn5.
► Hybridization of Zn-d and Sn-s state led to the stability improvement.
► Zn concentration corresponding to the most stable hexagonal Cu6(Sn,Zn)5 was 7.54 at%.