Syntheses and structures of the quaternary alkali-metal bismuth coinage-metal chalcogenides K_3Bi_5Cu_2S_(10), CsBi_2CuS_4, RbBi_(2.66)CuSe_5, and CsBiAg_2S_3

摘要

The four compounds K_3Bi_5Cu_2S_(10), CsBi_2CuS_4, RbBi_(2.66)CuSe_5, and CsBiAg_2S_3 were synthesized at 873 K by reactions of the elements in the reactive fluxes of A_2Q_3 (A=K, Rb, Cs; Q=S, Se). All crystallographic data were collected at 153 K K_3Bi_5Cu_2S_(10) crystallizes in the Rb_3Bi_5Cu_2S_(10) structure type in space group Pnnm of the orthorhombic system with two formula units in a cell of dimensions a=14.173(2) A, b=17.690(2) A, c=4.0362(5) A; CsBi_2CuS_4 crystallizes as a racemic twin in space group Cmc2_1 of the orthorhombic system with four formula units in a cell of dimensions a=4.0730(6) A, b=14.212(2) A, c=14.568(2) A; RbBi_(2.66)CuSe_5 crystallizes in a new structure type in space group Cmcm of the orthorhombic system with four formula units in a cell of dimensions a=4.1961(9) A, b=14.420(3) A, c=18.266(4) A; CsBiAg_2S_3 crystallizes in a new structure type in space group P2_1/c of the monoclinic system with four formula units in a cell of dimensions a = 13.3523(14) A. b =8.1052(8) A, c =6.9162(7) A, #beta# =99.766(2) deg. K_3Bi_5Cu_2S_(10), CsBi_2CuS_4, and RbBi_(2.66)CuSe_5 are related; they are all tunnel structures with the A atoms located in tunnels formed by BiQ_6 octahedra and CuQ_4 tetrahedra. CsBiAg_2S_3 is composed of two-dimensional (infinity)~2(BiAg2S_3~(1-)) layers separated by the Cs atoms. The (infinity)~2(BiAg2S_3~(1-)) layer is built from BiS_6 octahedra, linear AgS_2 groups, and AgS_4 tetrahedra.