Lanthanide Atoms Induce Strong Graphene Sheet Distortion When Adsorbed on Stone-Wales Defects

Local curvature in graphene can enhance its reactivity and catalytic activity and can be induced by the adsorption of certain chemical species. By employing periodic density functional theory (DFT) calculations, we demonstrate that significant local curvature can be systematically observed when lanthanide atoms (the full series from La to Lu) are adsorbed on the Stone-Wales (SW) defect in graphene, contrary to that in defect-free graphene. Despite the typical high coordination numbers of lanthanide species, their hapticity is always η² (and not η⁵, η⁶, or η⁷), where Ln atoms are adsorbed on the (7,7) junction, forming relatively short Ln···C separations. Contrary to the pristine graphene, the SW region undergoes considerable distortion and results in much stronger Ln bonding. The positive charge acquired by Ln atoms upon adsorption on SW is approximately 1.5 times larger than that on defect-free graphene. The high visibility of electron-rich lanthanide species in scanning tunneling microscopy images provides a means to locate SW defects in graphene samples experimentally.