Molecular Dynamics (MD) and Metropolis Monte-Carlo (MMC) models of monomer B and decaborane implantation into Si and following rapid thermal annealing (RTA) processes have been developed. The implanted B dopant and Si-atomic diffusion coefficients were obtained for different substrate temperatures. The simulation of decaborane ion implantation has revealed the formation of an amorphized area in a subsurface region, much larger than that of a single B+ implantation, with the same energy per ion. The calculated B diffusion coefficient has values between 10-12-10-10 cm2 s-1 which agrees well with experimental values obtained for an equilibrium B dopant in Si. Our calculations have shown an unusual temperature dependence with two different activation energies. Low activation energy, less than 0.2 eV, was obtained for a low-temperature region, and a higher activation energy, approximately 3 eV, for a higher-temperature region which is typical for the RTA processing. The higher activation energy is comparable with the equilibrium activation energy, 3.4 eV, for B diffusion in Si. The diffusivity for Si atoms was obtained to be in the interval 10-14-10-12 cm2 s-1. In our present simulation for decaborane cluster implantation into Si, we have not observed the TED phenomenon.