  We showed how a structural modification of graphene, which gives a carbon
allotrope graphyne, can induce an energy gap at the K point of the Brillouin
zone. Upon adsorption on metallic surfaces, the same mechanism is responsible
for the further modification of the energy gap which occurs via the charge
transfer mechanism. We performed the calculation based on the density
functional theory with the novel non-local vdW-DF correlation of the adsorption
of graphyne on Cu(111), Ni(111) and Co(0001) surfaces and showed the dependence
of the gap change on the charge transfer in the system. The binding of graphyne
appears to be stronger than of graphene on the same surfaces.
