The structure of a dissociated edge dislocation in copper is investigated. Attention is given to the structure of the Shockley partials and the equilibrium size of the fault ribbon. The studies are carried out through Molecular Dynamics simulations. The atomic interactions have been modelled through an Embedded Atom Model (EAM) potential. the implementation of which has been specially designed for this study. Our main results show that the equilibrium distance between partials is very sensitive to the type of boundary conditions imposed on the simulated system.