structures. The chlorine adsorbed on the bridged position at 0.5 ML coverage (Cl-Cl: 3.99, Cl-Fe: 2.31) showed a close analogy with bulk FeCl2 (Cl-Cl: 3.54, Cl-Fe: 2.47). They further demonstrated that substitutional chlorine adsorption on the iron surface is unfavourable indicating strong stability of Fe(100) surface and formation of iron chlorides via substitution is not possible. Inclusion of van der Waals (vdW) energy correction to the chlorine adsorption on Fe(100)