Simulation has been providing immense insight to understanding the dimerization process, aiding in the discovery of species that would not otherwise have been easily identified by experiment, and allowing the examination of molecular scale local effects. Simulation methods have grown in sophistication in parallel with the development of computing memory and processing power. The primary emphasis in the present study is on density functional theory methods (DFT) specifically, although other schemes that are in active development and application such as molecular dynamics and Monte Carlo have also been applied to investigate these mechanism. These other schemes are able to model chemical systems up to the micrometer scale that would not be practicable with DFT. However, the elucidation of chemical reactivity is still principally a question that is best handled on the atomic-length scale by DFT and ab initio methods in general because of the changes in bonding, and therefore electronic structure, during the course of a reaction. At the same time, it is worth noting that there are methods that algorithmically combine the strengths of both ab initio and molecular dynamics aptly named ab initio molecular dynamics .