8
2 Actual Potentials of Theoretical Chemistry: What Can Be Obtained
(a)
(b)
(c)
(d)
(e)
(f)
Fig. 2.5 Benzene and its isomers: a Benzene, b cyclohexatriene, c Dewar benzene, d benzvalene,
e prismane, and f fulvene. Hydrogen atoms are omitted
Fig. 2.6 Optimized molecular structures of a C 60 and b POSS: H 8 Si 8 O 12 . See Table 2.1 as to the
bond lengths and angles. These were optimized by DFT/B3LYP/6-31G**
Table 2.1. Meanwhile theoretical calculations for C 60 molecule have explosively
been accumulated to explain its peculiar structure itself as well as its electronic properties (Cioslowski 1995). It is thus helpful to guess the plausible shape of molecular
structure prior to or in parallel with the actual calculation as much as possible.
Moreover, the optimized structure of the modeled polyhedral oligomeric
silsesquioxane (POSS) molecule H 8 Si 8 O 12 in Fig. 2.6b has a caged structure with
O h symmetry. This molecule is used as a nanostructured material as pendants or
end-cappers to the polymers for the purpose of preventing the parent polymers from
aggregation (Xiao et al. 2003; Lee et al. 2004). Moreover, the electronic properties of
POSS molecule could be tuned by introducing organic functional groups connected