Theoretical study can offer a practical tool that provides clear
insight to the reaction mechanism complementing experimental
investigations or, in certain cases, offering an understanding that
is not possible by experimental investigations. Most of the
theoretical studies of chemical reactions on heterogeneous catalysts
are based on the use of wave function methods and density
functional theory (DFT). Wave function methods, especially
post-Hartree-Fock methods such as configuration interaction,
coupled cluster, and Moeller-Plesset perturbation theory, certainly
give accurate results. However, the high accuracy comes
with the price of higher computational cost. DFT has gained
increasing interest by providing good predictions of important
properties for a wide range of applications in chemistry with a
lower required computational demand. However, the conventional
DFT functionals are not able to properly describe van der
Waals effects, which are very important in the interactions of
host/guest systems. The selection of the functional in DFT is
crucial for correctly exploring the properties and reaction mechanisms
of chemical reactions. Considerable effort has been
invested to overcome this severe deficiency of DFT. Grimme9
has proposed a new semiempirical functional by introducing
atom-pairwise dispersion corrections to the generalized gradient