Packing studies

In many of the molecular packing studies, the crystal classes are taken from the experimental X-ray diffraction determinations. The optimal packing is then determined for the assumed crystal class. In other cases, the crystal classes have also been established in the optimization calculations. 

In general, performance data published in the literature are usually obtained from small laboratory equipment. As a result, efficiency and flooding correlations should be used with caution. The limits of models should be checked. For example, since most published packed extractor data are based on small diameter columns, the packings studied are usually small with a high specific surface area. The extrapolation of models primarily based on such high specific surface areas to larger packings with much lower areas... 

Our complementary approach combines the analysis of the crystal structure with analysis of the molecular structure of the component systems, using experimental data from X-ray crystal analysis, crystal packing studies, extended Hiickel and density functional calculations, as described above. 

The alternative route to intramolecular potentials, by crystal-packing studies, has been adopted for small hydrogen bonding moleeules. In a force field, lone pairs may be represented as electrostatic interactions, or by modifying torsional potentials. ... 

The bond lengths and bond angles for the molecules, methanol, acetic acid, and formic acid are given in Table III. The methanol geometry was taken from microwave spectroscopy [17], while the formic and acetic acid geometries were taken to be those of the dimers, found by gas phase electron diffraction [14-15, 13]. X-ray structural parameters were used for crystal packing studies of formic acid [32] and neutron diffraction data for acetic acid [33]. The hydrogen atoms for the molecules in their crystalline forms were positioned as described previously [46, 47]. 

If the relationship was solely dependent on diameter, then the behavior would tend to follow V = Sx + Jy in Fig. 17 more closely than it does. However, packing studies with larger spheres and plates would tend to suggest that V=Sx + Jy would be followed where electrostatic effects are insignificant. As plates are added into plate-sphere systems the tendency of the system to laminate increases markedly, leading to defects in the product. 

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