首页|On the possibility for Rb- and Eu-cation ordering in type-I clathrates: Synthesis and homogeneity range of the novel compounds Rb8-xEu x-(In,Ge)46(0.6 ≤ x ≤ 1.8)
On the possibility for Rb- and Eu-cation ordering in type-I clathrates: Synthesis and homogeneity range of the novel compounds Rb8-xEu x-(In,Ge)46(0.6 ≤ x ≤ 1.8)
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NSTL
Int Union Crystallography
Studies in the Rb-Eu-In-Ge system confirm the existence of the phase Rb8-xEux (In,Ge)46 (0.6 ≤ x ≤ 1.8), crystallizing with the cubic clathrate type-I structure. The In and Ge content can be varied, concomitant with changes in the Rb-Eu ratio. Two of the three framework sites are occupied by statistical mixtures of Ge and In atoms, while the site with the lowest multiplicity is taken by the In atoms only. Based on the three refined formulae [heptarubidium europium nonaindium heptatriacontagermanide, Rb7.39(3)Eu0.61(3)In 8.88(5)Ge37.12(5), and two forms of hexarubidium dieuropium decaindium hexatriacontagermanide, Rb6.30(3)Eu 1.70(3)In9.76(4)Ge36.24(4) and Rb 6.24(2)Eu1.76(2)In10.16(5)Ge 35.84(5)] and the explored different synthetic routes, it can be suggested that the known ternary phase Rb8In8Ge 38 and the hypothetical quaternary phase Rb6Eu 2In10Ge36 represent the boundaries of the homogeneity range. In the former limiting composition, both the (Ge,In) 20 and the (Ge,In)24 cages are fully occupied by Rb atoms only, whereas Rb6Eu2In10Ge36 has Rb atoms encapsulated in the larger tetrakaidecahedra, with Eu atoms filling the smaller pentagonal dodecahedra. For the solid solutions Rb8-xEu x(In,Ge)46, Rb and Eu are statistically disordered in the dodecahedral cage, and the tetrakaidecahedral cage is only occupied by Rb atoms.
NSTL
Int Union Crystallography
