Ab-initio calculations of fission product diffusion on graphene

A clear understanding of the diffusive behaviour of a wide variety of impurities is essential for the construction and safe operation of the class of nuclear reactors which employ graphite as a shielding material. As a means of gaining insight into this important problem, the bonding, activation energy and structural properties of a variety of the most common nuclear fission products on graphene have been examined using Density Functional Theory (DFT), illustrating the attendant mechanisms of bonding and ionic transport of the different species, as well as the tendency to form nanoscale clusters in bulk graphite. Simulations have been conducted using a variety of approximations to the exchange-correlation functional, and the relative importance of functional choice is discussed in the context of the adsorption and activation energies. Finally, our calculations are compared to the relevant experimental results, allowing us to draw some conclusions about the likely transport mechanisms at larger length and time scales.