Packing space

Depending on the size and packing (space group) of the asymmetric unit in the crystal and the resolution available, many tens of thousands of diffraction spots must be recorded to determine a structure. 

One-molecule unit cells are, however, not common. Usually there are two, four, or more molecules in the unit cell, and in such circumstances it is necessary to discover the manner of packing ( space-group symmetry —see pp. 241-51) before considering molecular dimensions. 

Atomic solids are often more dense than ionic solids. In ionic solids, ions of different sizes must be packed together. In this packing, spaces between ions make the solid less dense than atomic solids, where the atoms are uniform in size. 

Molecules of 43c adopt chiral packing (space group P2 ) and a helical molecular conformation, and crystallize in (E,Z) conformation which is unfavorable for the oxetane formation. The solid-state irradiation of 43c was found to give the oxetane 44c and a 3-lactam derivative 45c. The (3-lactam 45c was revealed to be enantiomerically enriched to 88% ee, whereas the other photoproduct 44c was racemic. The occurrence and the mechanism of transformation of 43c to 45c involve hydrogen abstraction by the alkenyl carbon atom. 

Systems of more than two components will possess a slightly greater degree of bulkiness except, as might be expected, when most of the material is extremely fine. In general, it may be said that mixtures of different-sized materials greatly increase the efficient use of packing space. The problem of proper proportions to obtain a minimum bulki ness can be approximated by methods previously outlined. 

The polymers of intrinsic microporosity (PIMs). These are rigid macromolecules composed of a fused-ring subunit which cannot pack space efficiently and hence form microporous materials (Figure 2.5) [68]. 

It is now common experience to use pressed pellets of inhibitor powders based on a polymer binder for packing and preservation of metal ware. They are easy to handle and can ensure prolonged isolation of the inhibitor inside the packing space. 

When introduced into the space between layers or in the middle layer of a multilayered film (Fig. 2.3e) the Cl can be isolated into the packing space at a controlled rate to ensure the rustproof environment, on one hand, and sufficient resource of the film material and safety, on the other [3[. 

Pol mier films containing VCI are said to be most promising means in inhibiting atmospheric corrosion of hardware, when evaporating VCI create a protecting atmosphere within the packing space. When impregnated into a... 

A cubic phase of space group Pmln is usually observed in type I systems [164]. Several structures have been suggested for the Pmln phase [168-171]. It is now agreed that it contains two types of micelles [172] two quasi-spherical micelles packed on a body-centered cubic lattice and six slightly asymmetrical micelles arranged in parallel rows on opposite faces of the unit cell. The asymmetrical micelles are assumed to be disklike [173] or rodlike with rotational disorder around one of the short axes [174,175]. In order to pack space completely, each asymmetrical micelle, together with the water that surrounds it, takes the shape of a... 

Since the packing space or container is digitised and represented in the same way as the particles, using a container with a complex geometry presents no additional difficulties. Moreover, just as a particle may be added at any time during packing, the container may be introduced or changed at any time. 

Table A. 11 Theoretical cluster size, based on simple geometrical models. The clusters are assumed to have a spherical or hemispherical shape and packing space of a fee packing is included or the Pt dimer distance in order to find to possible boundary conditions...

Table 23. Dimensions of Packing Spaces of Stuffing Boxes (Dimensions in mm)... 

Total height of packing Spacing between beds (9)(4 ft) Disengaging and distribution Reboiler... 

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