Stacking order

Zirconium chloride and bromide have closely related but dissimilar stmctures. Both contain two metal layers enclosed between two nonmetal layers which both have hexagonal stmcture. In ZrCl, the four-layer sandwich repeats in layers stacked up according to /abca/bcab/cabc/, whereas the ZrBr stacking order is /abca/cabc/bcab/ (188). Both are metallic conductors, but the difference in packing results in different mechanical properties the bromide is much more brittle. 

K. Otsuka, T. Ohba, M. Tokonami and C.M. Wayman, New description of long period stacking order... 

The stacking order of the lithium interlayers is aa (a Li-C6 -Li-C6 -Li chain exists along the c-axis) [84, 85], In LiC6 the lithium is distributed in-plane in such a manner that the occupation of the nearest-neighbor sites is avoided (Fig. 5b). 

A glance at the structure of graphite, illustrated in Fig. 1, reveals the presence of voids between the planar, sp -hybridized, carbon sheets. Intercalation is the insertion of ions, atoms, or molecules into this space without the destruction of the host s layered, bonding network. Stacking order, bond distances, and, possibly, bond direction may be altered, but the characteristic, lamellar identity of the host must in some sense be preserved. 

Water on Smectites. Compared to vermiculites, smectites present a more difficult experimental system because of the lack of stacking order of the layers. For these materials, the traditional technique of X-ray diffraction, either using the Bragg or non-Bragg intensities, is of little use. Spectroscopic techniques, especially nuclear magnetic resonance and infrared, as well as neutron and X-ray scattering have provided detailed information about the position of the water molecules, the dynamics of the water molecule motions, and the coordination about the interlayer cations. 

Fig. 15.1 The world energy supply in the two Shell long-term energy scenarios Dynamics as Usual and Spirit of the Coming Age. The stacking order is such that carbon-neutral electricity-delivering sources (hydro, nuclear and renewables excluding biofuels) are at the bottom. When overlaid with the energy demand of the electricity sector (lower hashed area) one observes that carbon-free electricity supply falls far short of electricity...

From Deer, R. A., W. A. Howie, and J. Zussman (1963). Rock-Forming Minerals, Polylype = the crystallographic designation of the stacking order of tetranedral and Layers display 4.35-nm corregation periods. 

Furthermore, the stacking order has been identified as that of the 3C-SiC polytype and, according to the stndy by Stahlbnsh, an explanation to the recombinative behavior of the stacking fanlt is that the 3C-SiC, having a lower bandgap than 4F1-SiC, acts as a qnantnm well, thereby enhancing the recombination [63]. It is a very serious materials issue that must be solved prior to the realization of commercial bipolar devices. 

In addition, analysts can create a multimodal SPE column by stacking several discs with differing bonded phase in the disc holder. With the proper chemical design, such multimodal systems can provide customized separation protocols. The stacking order of the discs depends on the particular physicochemical characteristics of the analysis under way. The general rule is to place the disc with the more selective extraction mechanism on top of the less selective adsorbent. 

Interpretation of two-dimensional images of sheet silicates has previously been addressed. Computer-simulated images of chlorite (22) and biotite and muscovite (2A) show that two-dimensional images of these sheet silicates allow determination of the basal spacing (spacing perpendicular to the sheets) and stacking order (relative rotations and shifts between sheets). Furthermore, these calculations show that at the Scherzer (optimum) focus, many, but not all, aspects of the structures may be interpreted directly. 

Further enhancement of jt-stacked order can be achieved by the use of small electron-withdrawing substituents. The 9,10-dihaloanthracenes (dichloro [31], di-bromo [32] and diiodo [33]) all adopt a jt-stacked arrangement in the solid, with... 

Fig. 14.10 9,10-Dimethyl-anthracene (14) and 9,10-bis(chloromethyl)anthracene (15), showing their solid-state Jt-stacking order. 

Fig. 14.40 6,13-Bis(triisopropylsilylethynyl)pentacene (55), showing two-dimensional Jt-stacked ordering in the crystal.

Over 25 million compounds are known, but only about one percent of them have their crystal structures elucidated by X-ray and neutron diffraction methods. Many inorganic structures are closely related to each other. Sometimes one basic structural type can incorporate several hundred compounds, and new crystalline compounds may arise from the replacement of atoms, deformation of the unit cell, variation of the stacking order, and the presence of additional atoms in interstitial sites. 

Figure 15. Graphitization of nanocrystalline graphene precursors (see Fig. 9). Chemical structures (dots represent heteroatoms or methyl groups) and stacking order are given as a function of characteristic temperatures. The polymerization and aromatization are reflected in the average lattice parameters which can be extracted from X-ray diffraction data. The correlation between the axis parameters indicates the shrinking of the cell volume [75].

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