Overall, we see that the absorption features of the pure Sn and Ti-based phases are maintained in the spectra of the mixed compositions, both experimentally and computationally, where the strong titanium peaks dominate until the Ti fraction drops below a certain concentration threshold at which the tin-based features emerge. This somewhat-uncommon behavior can again be ascribed to the weak and non-covalent metal-metal interactions in these systems, arising from the effectively zero-dimensional crystal structure with isolated BX 6 -2 octahedra. The lack of covalent metal-metal interactions in these vacancy-ordered perovskites results in minimal orbital hybridization or tuning of the electronic structure upon cation mixing, yielding this additive behavior for the properties of the mixed compositions -as also witnessed in Ref. 19.