Synthesis, crystal structures and chemical bonding of RE_5−xLi_xGe₄ (RE = Nd, Sm and Gd; x ≃ 1) with the ortho­rhom­bic Gd₅Si₄ type

Three members of the RE_5−xLi_xGe₄ (x ≃ 1) family have been structurally characterized. Their crystal chemistry mirrors that of RE_5−xMg_xGe₄ (x ≃ 2), and the valence electron count can be understood on the basis of the Zintl–Klemm formalism.

K and Ba distribution in the structures of the clathrate compounds K_xBa_16-x(Ga,Sn)₁₃₆ (x = 0.8, 4.4, and 12.9) and K_xBa_8-x(Ga,Sn)₄₆ (x = 0.3)

Four clathrates with type-I and type-II structure are reported in the K-Ba-Ga-Sn system. For the type-I compound, all framework sites are occupied by a mixture of Ga and Sn atoms, with Ga showing a preference for Wyckoff site 6c. For the type-II structures, only the smaller (Ga,Sn)₂₄ penta­gonal dodeca­hedral cages are filled, while the (Ga,Sn)₂₈ hexa­kai­deca­hedral cages remain empty.

Ternary K₂Zn₅As₄-type pnictides Rb₂Cd₅As₄ and Rb₂Zn₅Sb₄, and the solid solution Rb₂Cd₅(As,Sb)₄

Rb₂Cd₅As₄ and Rb₂Zn₅Sb₄ are new ternary pnictides with a complex orthorhombic structure. In the absence of homoatomic interactions, the chemical bonding can be understood as (Rb⁺)₂(Cd²⁺)₅(As^3-)₄ and (Rb⁺)₂(Zn²⁺)₅(Sb^3-)₄, respectively, following the Zintl concept.

On the possibility for Rb- and Eu-cation ordering in type-I clathrates: synthesis and homogeneity range of the novel compounds Rb_8–xEu_x(In,Ge)₄₆ (0.6 ≤ x ≤ 1.8)

Clathrates with the type-I structure are reported in the quaternary Rb–Eu–In–Ge system. Possible cation ordering is suggested.