Atomic site parameters, optimization

As it follows from Table 1, a jr-charge of over le is concentrated on the carbon atoms. Therefore, each carbon atom can be in principle an adsorption site. The optimization of the position of oxygen atoms relative to the surface was performed at frozen geometric parameters of the PANI cluster. Calculations of the adsorption of molecular oxygen on PANI showed that the carbon atoms of the phenyl ring, which are shown by Figure 4, are the most stable surface adsorption sites (AS). 

Visual analysis oi Figure 7.14 immediately indicates that the agreement between the observed and calculated intensity is poor. Furthermore, Rietveld refinement of this model of the crystal structure, during which the coordinates of atoms in the 4(e) site plus population of 4(d) and 4(e) sites were optimized together with the overall isotropic displacement parameter, results in the removal of Rh atoms from all sites population of both sites by Rh becomes negative (see the data file Ch7Ex02c.inp on the CD). 

The program is reported to carry out simple Hiickel molecular orbital calculations to determine the relative sensitivity of aromatic carbon atoms to oxidation and the relative stability of keto and enol tautomers. Klopman et al. (1999) have reported that for polycyclic aromatic hydrocarbons, adequate reactivity is an essential but not sufficient condition for enzyme catalyzed reaction. The accessibility of the reactive site (i.e., the absence of steric hindrance) was also found to be important. Genetic algorithms have been used to optimize the performance of the biotransformation dictionary by treating the initial priority scores set by expert assessment as adjustable parameters (Klopman et al., 1997). 

To describe the adsorption structures, we first label the atoms of the As dimers as Ass for the two side dimers, AsM for the dimer atoms in the middle and Asu for the unsaturated As atoms in the second layer, as shown in Figure 15-13. The covalent bonds formed between a fullerene and the two Ass atoms of both sides are denoted by a and 8, respectively, and the bond formed between a fullerene and the AsM atom is labeled as Finally, the covalent bonds between a fullerene and the Asu atoms are labeled as (3 and 7, respectively. Here, a, (3,7,8, represent not only bonds but also the close contacts. The labeling scheme is shown in Figure 15-13. We now concentrate on the adsorption of C32 through C60 only at the T site. The main optimized structural parameters and bonding situation are shown in Table 15-3. 

Fig. 7 and Tables 4 and 5 summarize the optimized geometry and energy parameters for the C C ) complex. Two different sites (Type A and Type B) for the endohedral carbon atom were found. The first position is near the center of the five-member faces of the fullerene molecule, while the second one is slightly shifted fixjm the center of the six-member face in the direction of the neighboring five-member face (the B3LYP/6-31G(d) level of theory). 

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