- © 2014 E. Schweizerbart'sche Verlagsbuchhandlung Science Publishers
The synthetic analogue of the mineral tischendorfite, Pd8Hg3Se9, was prepared using the silica glass tube technique and its crystal structure was solved and refined from powder X-ray diffraction data. The structure is orthorhombic, space group Pmmn, with a = 7.1886(2), b = 16.8083(5), c = 6.4762(2) Å, V = 782.51(4) Å3 and Z = 2. There are three Pd, two Hg and four Se independent positions. Tischendorfite crystallizes in a framework structure, where Pd atoms show two types of coordination by Se atoms: [PdSe4] squares and [PdSe5] pyramids. The [PdSe5] pyramid shares two opposite Se–Se edges with adjacent pyramids forming linear isolated chains running along the a-axis, whereas [PdSe4] squares are paired via one common Se–Se edge. The paired squares and chains of pyramids form characteristic slabs parallel to (010). Both types of slabs alternate along the b-axis. The Hg atoms occupy the anti-cubooctahedral voids formed by Se atoms. The structure is stabilized by a system of Pd–Hg and Pd–Pd metallic bonds.