Structural, Electronic, and Optical Properties of K 2 Sn 3 O 7 with an Offset Hollandite Structure.

We present the compound K2 Sn3 O7 , a Sn4+ -containing oxide with a unique structure type among oxides. The compound is orthorhombic and reminiscent of an offset hollandite, where open channels hold a row of four K+ per channel per cell. UV-visible spectroscopy indicates a wide band gap semiconductor, which is confirmed by first-principles electronic-structure calculations of band structures, densities of states, and optical properties. The continued discovery of new structure types in ternary tin oxides should remain a priority for the identification of prospective ion conductors and transparent conducting compounds.