The crystal structure of tedhadleyite, Hg2+FormulaO4I2(Cl,Br)2, from the Clear Creek Claim, San Benito County, California

摘要

The crystal structure of tedhadleyite, ideally Hg2+O₄I₂(Cl,Br)₂, triclinic, A, a 7.0147(5), b 11.8508(7), c 12.5985(8) Å, 115.583(5), β 82.575(2), 100.619(2)°, V 927.0(2) Å3, Z = 2, was solved by direct methods and refined to an R₁ index of 4.5% for 2677 unique reflections. There are six symmetrically distinct Hg sites in tedhadleyite: Hg(1) is occupied by Hg2+ and Hg(2-6) are occupied by Hg+ that forms three [Hg-Hg]2+ dimers with Hg-Hg separations between 2.527 and 2.556 Å. These [Hg-Hg]2+ dimers have strong covalent bonds to O atoms, forming pseudo-linear O-Hg-Hg-O arrangements, and weak bonds to halogen and O atoms at high angles to the dimer axis. The [O-Hg-Hg-O] groups share anions to form four-membered square rings of composition [Hg₈O₄] that link along [100] via [O-Hg-Hg-O] groups and along [001] via [O-Hg-O] groups, forming rectangular rings of composition [Hg₁₄O₈]. The rings form a corrugated layer that interweaves with a symmetrically related layer whereby the [O-Hg(6)-Hg(6)-O] linking groups of one layer pass through the centres of the square [Hg₈O₄] rings of the other layer to form [Hg₁₁O₄] complex slabs parallel to (010) that link through Hg-I and Hg-Br,Cl bonds.