Figure 5

(a) A close-up view of H-bonding between a phenol group and a carboxylic anhydride group as predicted from the MD simulations of soot with the COMPASS force field. The interlayer spacing is controlled by π–π interactions, but this result indicates that H-bonding between layers may contribute to the bonding energy as well, (b) MP2/6-31G* calculation[20] of H-bonding between phenol and carboxylic anhydride used to test the result of the COMPASS-based MD simulation shows similar H-bonding behavior. High-level molecular orbital theory calculations such as these are not possible on large molecules such as the soot model, but small fragments of the larger molecules may be modeled using this type of quantum mechanical calculations. Graphics generated with CrystalMaker.[34]