Consecuencias geom\'etricas y din\'amicas de la m\'ultiple adsorci\'on de Litio y otros alcalinos en poliacenos, poli-parafenilenos y hojuelas de grafeno

TL;DR

This study investigates how lithium and other alkali metals induce symmetry breaking in polyacenes, poly-para-phenyls, and graphene-like structures, revealing Peierls distortion effects and implications for chemical reactions on graphene surfaces.

Contribution

It demonstrates that lithium induces Peierls distortion in small polyacenes, providing insights into symmetry breaking mechanisms relevant to graphene-like materials.

Findings

Lithium causes spontaneous symmetry breaking in polyacenes via Peierls distortion.

Other alkali metals do not induce symmetry breaking in polyacenes.

Peierls distortion is limited to small flakes and does not extend to larger graphene structures.

Abstract

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.