Computational Design of Perovskite Ba x Sr1– x SnO3 Alloys as Transparent Conductors and Photocatalysts

Using a first-principles-based multiscale computational approach involving density functional theory and the cluster expansion method, we produced the structural evolution for the perovskite BaxSr1–xSnO3 system in relation to its Ba:Sr composition from the formation energies of different alloy configurations and demonstrated their use as tunable alloy transparent conductors and photocatalysts via structural, electronic, and optical studies. The predicted phase diagram revealed the transformation of the structure of BaxSr1–xSnO3 from orthorhombic to tetragonal and finally to cubic with increasing x, forming disordered solid solutions for 0 < x < 1 that is entropically stabilized against phase segregation. This trend is similarly observed in the published experiments. A special quasirandom structure approach is used to model the disordered solid solutions of the BaxSr1–xSnO3 alloys. Structural analyses have indicated that the decrease in Ba:Sr ratio is associated with the decrease in unit cell volume, and also the increased distortion of the (Ba,Sr)­O12 cuboctahedra, while the SnO6 octahedra remained relatively undistorted and underwent tilting to accommodate the smaller Sr atoms. Electronic and optical studies have shown the BaxSr1–xSnO3 alloys to possess transparent conducting, photocatalytic water splitting and CO2-reduction capabilities, which can be tailored via compositional engineering. The results should serve as a guide for the investigations of structure–property relationships of perovskite-based alloys.