Carbon dioxide clusters structure

Transition metal catalysts, specifically those composed of iron nanoparticles, are widely employed in industrial chemical production and pollution abatement applications [67], Iron also plays a cracial role in many important biological processes. Iron oxides are economical alternatives to more costly catalysts and show activity for the oxidation of methane [68], conversion of carbon monoxide to carbon dioxide [58], and the transformation of various hydrocarbons [69,70]. In addition, iron oxides have good catalytic lifetimes and are resistant to high concentrations of moisture and CO which often poison other catalysts [71]. Li et al. have observed that nanosized iron oxides are highly active for CO oxidation at low tanperatures [58]. Iron is unique and more active than other catalyst and support materials because it is easily reduced and provides a large number of potential active sites because of its highly disordered and defect rich structure [72, 73]. Previous gas-phase smdies of cationic iron clusters have included determination of the thermochemistry and bond energies of iron cluster oxides and iron carbonyl complexes by Armentrout and co-workers [74, 75], and a classification of the dissociation patterns of small iron oxide cluster cations by Schwarz et al. [76]. 

In the case of calcined kaoUn, individual kaolin plates are thermally fused into a clustered shape. With scalenohedral and aragonitic PCC, either a rosette or repetitive needle structure is formed through carefully controlled reactions of milk of lime and carbon dioxide. Amorphous silica products are chemically aggregated into repeating silica rings. 

To begin how small is small For our purposes we shall take a small cluster to have a comparable number of molecules on the exterior as the interior. Two such examples are shown in Fig. 6. In one case we have presented a cluster of ( 02) where the structure is consistent with that for bulk crystalline carbon dioxide. Electron diffraction studies of clusters of this size suggest that this is a reasonable structure. Infrared spectra of small clusters is also consistent with the proposed geometry. As Miller et al. show, the structures of (C02>2 and (002)3 bear no clear relationship to that of the bulk crystal. 

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