Weberite

Weberites. If the metal positions of the (6,3)-net above (Figure 28(a)) are occupied in an ordered way by cations forming trans-chains and by linking M ions, the typical layer of weberites is achieved (Figure 29(a)). Additional... 

Figure 29 (a) Kagome net formed by [M Fe] (bright) and [M "Fg] (dark) octahedra (b) O-I weberite structure of Na2NiAlp7. View along the M" octahedral chains, Na grey spheres... 

Figure 30 Cation distribution in (a) Cap2 and (b) weberite O-I (white Na, grey M , black M )...

Pyrochlore- and RbNiCrFg-Type Structures. Closely related to the weberite variants are pyrochlores AA M2Fv (A = Na, A = Ca, Cd M = Mg, Co, Ni, Cu, Zn). Here, all octahedra are equivalent and the cubic 3D network can be described as intersecting systems of Kagome nets with planes parallel to the faces of a tetrahedron. Another approach is the description as cross-linked octahedral chains where at the crossing points typical tetrahedra of comer-connected octahedra are generated (Figure 31). 

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