First-principles study of the structural and electronic properties of Sr1−xMxSi2 (M=Ca and Ba)
We investigated the structural and electronic properties of Sr[Formula: see text]M[Formula: see text]Si2 (M[Formula: see text]=[Formula: see text]Ca and Ba) (x[Formula: see text]=[Formula: see text]0, 0.25, 0.5, 0.75 and 1) by the first-principles calculation in the frame work of density-functional theory. It was found that the structure of Sr[Formula: see text]Ca[Formula: see text]Si2 is evidently compressed with increasing the Ca content. On the other hand, the incorporation of Ba cause the swelling crystal structure. A structure transition for Sr[Formula: see text]M[Formula: see text]Si2 (M[Formula: see text]=[Formula: see text]Ca and Ba) from cubic to tetragonal appear when the doping concentration is 0.5. Band structure calculations indicated that the bandgap decrease or even disappear with increasing Ca atoms, which suggesting the transition from the semiconductor to the metal for SrSi2. Whereas, the semiconducting bandgap increases with the incorporation of Ba atoms. Our results imply that the thermoelectric properties of SrSi2-based alloys can be further enhanced by increasing Ca doping content, Ca-doped SrSi2 is a promising thermoelectric material.