  Results of first principles modelling of interactions graphene and graphite
with iron impurities predict the colossal difference between these two carbon
allotropes. Insertion of the iron atoms between the planes of graphite is much
more energetically favourable than adsorption of the iron adatom at graphite or
graphene surface. High mobility of iron adatom over graphite surface and within
bulk graphite is reported. Calculated values of formation energies for the
substitutional iron impurities suggest that iron is more destructive for
graphite than for graphene. This effect caused formation of uniform carbon
environment of the iron atom inside the multilayer system. In contrast to
graphene segregation of the substitutional iron impurities in graphite at the
ambient conditions is not energetically favourable. Enhancement of interlayer
bonding in contaminated graphite and purity of graphene from iron impurities
are also reported.
