title: Ca6Cu2Sn7: novel 3D open framework with unusual Sn4 tetramers.
abstract: The new ternary polar intermetallic phase, Ca6Cu2Sn7, has been synthesized by the solid-state reaction of the stoichiometric mixture of the pure elements in welded Ta tubes at high temperature. Its structure was established by single-crystal X-ray diffraction studies. Ca6Cu2Sn7 crystallizes in the monoclinic space group C2/m (No. 12) with cell parameters of a=14.257(7), b=4.564(2), and c=12.376(7) A, beta=93.979(6) degrees, V=803.3(7) A3, and Z=2. The structure of Ca6Cu2Sn7 belongs to a new structure type and features a 3D anionic open-framework composed of [Cu2Sn3] layers interconnected by unusual Sn4 tetramers, forming large tunnels along the b axis which are composed of Cu4Sn12 16-membered rings. The calcium atoms are located in these large tunnels. Ca6Cu2Sn7 is metallic and exhibits temperature-independent paramagnetism.
authors.affiliation: State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, P. R. China.
authors.forename: Zhong-Ming
authors.initials: ZM
authors.lastname: Sun
authors.forename: Sheng-Qing
authors.initials: SQ
authors.lastname: Xia
authors.forename: Yi-Zhi
authors.initials: YZ
authors.lastname: Huang
authors.forename: Li-Ming
authors.initials: LM
authors.lastname: Wu
authors.forename: Jiang-Gao
authors.initials: JG
authors.lastname: Mao