Polyhedra stacking

Silanation reaction of silane (SiELi) with OH groups Sorption uptake of liquid or gas by a microporous material Space-filling spatial arrangement of polyhedra such that each polyhedron shares all its faces with other polyhedra Stacking fault misalignment of layer(s) arising from a fault plane... 

Figure 2.29 The TPTZ ligands stack to form a centrosymmetric dimer in the crystal structure of Eu(L )3TPTZ. [25]. (Reprinted from Polyhedron, 26, C.R. De Silvaa, J.R. Maeyera, A. Dawsona and Z. Zheng, Adducts of lanthanide -diketonates with 2,4,6-tri(2-pyridyl)-l,3,5-triazine synthesis, structural characterization, and photoluminescence studies, 1229-1238, 2007, with permission from Elsevier.)...

A similarly complicated structure is found in [Fei2(0)2(0Me)ig(02CMe)6-(EtOH)3] 48 [43], where there again two stacked butterflies linked by tetrahedra (Figure 23). Here the tetrahedra contain one wing-tip iron from each butterfly, with two further atoms completing the polyhedron. The tetrahedra are now capped on three faces by /rg-methoxides, with the fourth face occupied by a jU4-oxide. The butterfly units are distorted because these jU4-oxides occupy the sites where one of the two /i3-oxides would be expected, but are displaced towards the tetrahedra. 

Figure 65. The crystal structures of nefedovite and olgite (a) nefedovite projected onto (100) (b) nefedovite projected onto (001) (Na( )n) polyhedra are daik-shadow-shaded, (Ca( )8) polyhedra are light-shadow-shaded (c) (SrOi2)-icosahedron layer in olgite projected onto (001) (d) the (Sr,NaOio)-(Na07)-polyhedron layer in olgite projected onto (001) (e) the stacking of layers along [001] in olgite (S n) icosahedra are dark-shadow-shaded, (NaOio) polyhedra are dark-shaded, (NaOe) octahedra are dot-shaded.

At AnXa stoichiometry there are four families of binary intermetallic compounds, which represent different stacking schemes of the close-packed layer shown in Fig. 19.6(a) [34]. All stacking variants yield crystal structures in which a CN 12 polyhedron consists entirely of X atoms surrounding the An atom. The structures that occur are the AuCus, TiNis, MgCdj, and PuAls types. The AuCus-type structure, ordered fee, is the most prevalent, occurring particularly when the actinides combine with Rh and Pd the other three structure types are ordered variants of the hep structure. 

Fig. 233. The cation coordination polyhedron in Ce2SeF4. The stacking sequence of the hexagonal layers is indicated on the right.

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