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Published online by Cambridge University Press: 01 February 2011
We describe the Tl2SnAs2Q6, (Q= S, Se) compounds which consist of [SnAs2S6]2- layers with the Tl+ cations lying in between. Tl2SnAs2S6 and Tl2SnAs2Se6 crystallize in the space group P-3 with a = 6.706(4) Å, c = 7.187(6) Å and a = 6.996(3) Å, c = 7.232(4) Å respectively. These compounds are semiconductors with band gaps of 1.68 eV for the sulfide and 1.08 eV for selenide corresponding to their dark red and black colors respectively. Band structure calculations suggest indirect band gaps in these materials.