An MD simulation to form an NV-N center using N2 implantation into diamond

We have examined the dissociation process of a low-energy molecular beam making use of an empirical molecular dynamic simulation. The main concern was to explain why two (nitrogen molecule N₂) beams with different energy (sub-keV and keV) give a similar intrapair distance R_N-N in diamond. It was due to the peculiar dependence of the lateral range straggling on the incident energy across a few keV. When a sub-keV (N₂) beam was implanted into a diamond, the dissociation elapsed a long time until it was settled in several hundreds fs because of multiple collisions. The range distribution caused by multiple collisions is almost isotropic whereas it becomes anisotropic when used a (N₂) beam with the higher energy than that. From the viewpoint of computation, a few keV is a critical energy to choose an algorithm MD or MC with binary collision approximation. For the case of sub-keV N₂ beam, MD is indispensable. This proved the reason of the apparent contradiction. Much later than the collision stage, a definite change further occurred in the long-range-order of the crystal at around 2 ps in diamond. It seems a phonon-assisted phenomenon would start then and might affect on the further events to be occurred later than 20 ps.