In this diploma work the diffusion of dehalogenated organic molecules on a metal surface was studied. More specifically the benzene tri-radical (BTR) on Ag(111) surfaces has been computationally studied using density functional theory calculations. The diffusion of organic molecules on metal surfaces is one of the key parameters in the on-surface synthesis of covalent materials. Transition-states of different diffusion paths were calculated with the nudged elastic band (NEB), climbing image nudged-elastic band (CI-NEB) and Dimer methods. During the diffusion process, bonds are subsequently broken and forming between the molecule and the surface. The diffusion mechanisms were carried out between different adsorption sites, and the diffusion type with lowest barrier was identified.