Equilibrium concentrations of the major species in conventional and halogen assisted CVD diamond synthesis systems were calculated and the results are presented in this thesis. The optimal diamond deposition conditions were predicted based on these calculations and kinetic considerations as well. The calculations suggest that the addition of chlorine or fluorine can significantly reduce the temperature of CVD diamond deposition. The step growth mechanism on a diamond (001) surface was also investigated using molecular mechanics calculations (MM3). The basic step in diamond growth was found to be the incorporation of a gas phase carbon species such as the methyl radical into two carbon atoms on the surface which involves the breaking of the original dimer bond and the formation of a new one. It is suggested that only growth on the S\sbB step can continuously generate a smooth (001) surface while individual dimer rows extending from the S\sbA step or random dimer rows are kinetically unstable. The mechanism presented in this thesis explains the recent STM observations of finger growth patterns which extend from the SB step on the diamond (001) surface.