THE CRYSTAL STRUCTURE OF SYNTHETIC RADTKEITE, HG3S2CLL

Abstract

The crystal structure of the artificial analogue of the rare mineral radtkeite, Hg(3)(2+)S(2)Cll [monoclinic, space group C2/m, Z = 8, a 16.827(4), b 9.117(1), c 13.165(5) Angstrom, beta 130.17(2)degrees, V 1543.2(7) Angstrom(3)] has been solved by direct methods, and refined to an R index of 5.27%, on the basis of 1498 unique reflections (R-int = 0.0254) measured with MoKalpha radiation on a CAD-4 automated diffractometer. The transformation (a) over right arrow (orth)' = (a) over right arrow (m) + 2 (c) over right arrow (m), (b) over right arrow (orth)' = (a) over right arrow (m) + 2 (c) over right arrowm 20.120(4) Angstrom, and (c) over right arrow (orth)' = (b) over right arrow (m) and produces a pseudo-orthorhombic F-cell, in which alpha(o)' = beta(o)' = 90degrees, and gamma(o)' differs slightly from 90degrees (89.55degrees). Close agreement of these cell dimensions with those reported for natural radtkeite confirms the identity of these compounds, as does the good match between calculated X-raydiffraction patterns and the powder-diffraction pattern of natural radtkeite. The structure contains five independent mercury atoms; each Hg2+ is covalently bonded to two sulfur atoms at a distance of 2.240(6)-2.474(8) Angstrom; the angles S(2)-Hg(1)-S(2)' and S(1)-Hg(3)-S(1)' equal 177.9(4) and 180.0(3)degrees, respectively. The angles S(2)-Hg(5)-S(1) [146.1(2)degrees], S(1)-Hg(4)-S(1)' [161.8(3)degrees] and S(2)-Hg(2)-S(2)' [164.3(3)degrees] deviate greatly from linearity. Corrugated [Hg12S8](infinityinfinity) layers are parallel to (001) in the structure. Halogen atoms are located inside and between the [Hg12S8](infinityinfinity) layers, at Hg-Cl and Hg-I distances of 2.783(7)-2.961(6) and 3.167(4)-3.231(2) Angstrom, respectively.