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Synthesis, Crystal and Electronic Structures, and Physical Properties of Caged Ternary Cu-Rich Antimonide: BaCu 7.31(3) Sb 5

2010; American Chemical Society; Volume: 49; Issue: 16 Linguagem: Inglês

10.1021/ic100790r

1520-510X

Wu‐Zui Zheng, Peng Wang, Li‐Ming Wu, Ling Chen,

Iron-based superconductors research

A new caged Cu-rich antimonide, BaCu(7.31(3))Sb(5), was obtained from a direct combination of the elements in a graphite crucible under a high vacuum by a solid state reaction, and the structure was determined by the single-crystal X-ray diffraction method to be hexagonal P6(3)/mmc (No.194), with a = 7.0154(4) A, c = 12.5423(14) A, V = 534.58(7) A(3), and Z = 2. BaCu(7.31(3))Sb(5) is the first antimonide member of the BaNi(9)P(5)-type barium copper pnictides with a Cu2 site occupancy of 43.7(9)%, and the structure building unit is a 30-vertex Cu(18)Sb(12) cage centered by a Ba atom. The Cu(18)Sb(12) cages form chains along the c axis by sharing the opposite hexagonal (Cu2)(3)(Sb2)(3) faces. Such a cage chain shares (Cu1)(2)(Sb1)(2) rhomboidal faces with six neighboring chains along the [100], [010], and [110] directions to generate a 3D condensed metallic network. The electronic structure calculations by CASTEP indicate the metallic nature, which matches well with the metallic electrical conductivity, small Seebeck coefficient, and Pauli paramagnetism. The calculated formation energies indicate that BaCu(7.5)Sb(5)[triple bond]Ba(2)Cu(15)Sb(10) with the Cu2 site half occupied is the energetically favorable stoichiometry compared with Ba(2)Cu(12)Sb(10) (empty Cu2 site) and Ba(2)Cu(18)Sb(10) (fully occupied Cu2 site).