Abstract
With the methodologies presented here, the combined QM/MM method and the ab initio molecular dynamics method, we are moving towards more realistic computational models. The QM/MM method allows for the simulation of large systems at the ab initio level without completely neglecting the groups and substituents not within the active site. As demonstrated by our QM/MM calculations of the Brookhart Ni(II) based polymerization catalyst, these outer groups can often play a crucial role in the chemistry. Since the stereoselectivity in many catalytic systems is controlled by steric interactions there is great potential for the combined QM/MM method to be utilized effectively in such areas. The ab initio molecular dynamics method also shows great potential for becoming a standard computational chemistry tool particularly for exploring processes which have a high degree of configurational variability. We have applied the methodology to several transition metal based homogenous catalytic systems, clearly demonstrating the usefulness of the method. With electrostatic coupling, the combed QM/MM molecular dynamics method is a very promising tool for including solvent effects. Indeed with the combination of these techniques we are developing more sophisticated models of catalytic systems which can take into account large ligands, finite temperature effects and potentially solvent effects.