Crystal chemistry, DFT calculation and optical properties of the double perovskite stannate Sr2Sn0.8In0.8W0.4O6

•Combination of µ and τ factors predicts the formability of double perovskite Sr2Sn0.8In0.8W0.4O6•DFT calculations predict that it should be assigned to the class of semimetals•Co-substitution of In3+ and W6+ at the Sn4+ site do not experimentally affect gap of SrSnO3•Conduction band of Sr2Sn0.8In0.8W0.4O6 is not dominated by contributions of the W 5d-like•Presence of carbonates and water molecules due to moisture-swing sorption