Elements that from double halide perovskites with the A₂B¹⁺B³⁺X₆ composition. Light blue element indicates that at least one compound with a double halide perovskites structure containing that element has been synthesized. The triangular color tag indicates the site occupied by that element, according to the legend at the top. Au is half-colored because it exists only in A₂Au₂X₆ with A = Rb, Cs and X = Cl, Br, I. Reprinted with permission.^[79]