Refinement of SnS₂ polytypes 2<i>H</i>, 4<i>H</i> and 18<i>R</i>

Abstract

The 2H, 4H and 18R polytype structures of SnS2 have been refined using X-ray single-crystal data. Chemical analysis, density measurements and the refined structure models show that the 4H and 18R polytypes have stoichiometric compositions, whereas the composition of the 2H polytype is SnS2_x (0.15 -- x __ 0.18). The occupancies of the hexagonal S and Sn layers vary within the range 0-8-1.0 and are modulated in the stacking direction. Space group P3ml (No. 164) was assigned to the 2H, P3ml (No. 156) to the 4H and R3m (No. 166) to the 18R polytype. The structures have been refined to R = 0.013, wR = 0-019 for the 2H, R = 0.026, wR = 0.030 for the 4H and R--0.056, wR = 0.056 for the 18R polytype using 99, 552 and 422 unique reflections, respectively. Crystal data at room temperature: Mr = 182-90, a2t-/= a4H = algR = 36470 (8), CZH = 58990 (5), C4/~ = 11811 (2), C~SR = 53118(7)A; Z2H =1, ZaH= 2, ZI8R = 9, V2H = 6798 (4), VnH= 13611 (8), V~8R = 6121 (3)A 3, Dmz,= 34 (2), Om4 H = 4-1 (1), Dml8R = 39 (1) Mg m -3, Mo Keg, ,~ =