Aggregation models computational results

Table 2.7 gives the computational results from the aggregation model. 

These procedures not only indicate the kinetics of aggregation, but also allow study of the size distribution and the fractal geometry of the clusters. Typical results for the fractal dimension of clusters grown in computer simulations are summarized in Table 5. Note that the monomer-cluster aggregation models produce dense nonfractal clusters, except for the diffusion-limited case, whereas cluster-cluster models yield fractal dimensions in good agreement with experiments on real colloids. 

For example, studies of the morphology of a number of flame-generated aggregates (different carbonaceous soots, A1203 aerosols, etc.) [203] by both TEM and ALS procedures resulted in D2 = 1.7 0.15, while analysis of silhouettes of computer models of seven proteins [211] gave a value of D2 = 1.120 0.025, etc. 

The atomic density of the hex phase is about 20% higher than that of the 1 x 1 phase. As could be demonstrated by scanning tunneling microscopy (STM) (49), during the CO-induced hex — 1 x 1 transformation, these additional atoms are squeezed out from the surface layer, on top of which they are aggregating to new small I x 1 patches, a result which could also be successfully modeled by computer simulations (50). 

Ab initio and density functional theory (DET) methods have been exploited to determine the structures and the interaction energies of 2/7-isoxazol-5-one B, and its dimer and trimer structures in the gas phase. For the cyclic trimer, the computed structural parameters resulted in excellent agreement with the X-ray determination of the supramolecular aggregate of 4-(2-methoxybenzyl)-3-phenyl-4//-isoxazol-5-one, involving very strong intermolecular H-bonds of the NH tautomeric form, interpreted in terms of the RAHB (resonance-assisted hydrogen bond) model (see Section 4.03.3.1) <2002HCA2364>. 

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