  We study the spontaneous symmetry breaking due to adsorption of Lithium atoms
on polyacenes and aromatic molecules consistent on carbon rings with edges
closed by bond of hydrogen atoms. Hartree Fock and DFT calculations were made
for polyacenes, poly-para-phenyls and carbon sheets of sizes that show
properties of graphene. As a result, the spontaneous symmetry breaking on
polyacenes due to the adsorption of multiple pairs of Lithium atoms on opposite
sides find expla- nation on the Peierls distortion. We also found that there
are no sponta- neous symmetry breaking due to adsorption of other alkalines in
polyacenes and the only case showing a distortion of polyacene is when a pair
of Sodium atoms is adsorbed on it. Although there were previous studies about
adsorption of metals on lar- ge sheet of carbon, we initially wanted to
simplify the problem so that allowed us to obtain a better understanding of the
reasons for symmetry breaking and then extend it to complex structures, for
which, we found that the Peierls distortion is observable in small flakes, with
appropriate symmetry, but can not be generalized to larger flakes and neither
graphene strips as the minimum energy states of these cases do not correspond
to this distortion. As an application on the methods we have used in the
present work, a me- chanism for the decomposition reactions of chloromethane,
dichloromethane and formyl chloride on graphene surface is proposed. For this,
we calculate the reactions on the graphene surface with a Lithium atom absorbed
on the center of it at the opposite side and we found intermediate production
of radicals is reduced.
