Browsing by Subject "81.16.Pr"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item Open Access Domain formation on oxidized graphene(American Physical Society, 2012-11-01) Topsakal, M.; Çıracı, SalimAbstract Using first-principles calculations within density functional theory, we demonstrate that the adsorption of a single oxygen atom results in significant electron transfer from graphene to oxygen. This strongly disturbs the charge landscape of the C-C bonds at the proximity. Additional oxygen atoms adsorbing to graphene prefer always the C-C bonds having the highest charge density and, consequently, they have the tendency to form domain structure. While oxygen adsorption to one side of graphene ends with significant buckling, the adsorption to both sides with similar domain pattern is favored. The binding energy displays an oscillatory variation and the band gap widens with increasing oxygen coverage. While a single oxygen atom migrates over the C-C bonds on the graphene surface, a repulsive interaction prevents two oxygen adatoms from forming an oxygen molecule. Our first-principles study together with finite-temperature ab initio molecular dynamics calculations conclude that oxygen adatoms on graphene can not desorb easily without the influence of external agents.Item Open Access Graphene coatings: an efficient protection from oxidation(American Physical Society, 2012) Topsakal, M.; Şahin, H.; Çıracı, SalimWe demonstrate that graphene coating can provide efficient protection from oxidation by posing a high-energy barrier to the path of oxygen atom, which could have penetrated from the top of the graphene to the reactive surface underneath. A graphene bilayer, which blocks the diffusion of oxygen with a relatively higher energy barrier, provides even better protection from oxidation. While an oxygen molecule is weakly bound to a bare graphene surface and hence becomes rather inactive, it can easily dissociate into two oxygen atoms adsorbed to low-coordinated carbon atoms at the edges of a vacancy. For these oxygen atoms the oxidation barrier is reduced and hence the protection from oxidation provided by graphene coatings is weakened. Our predictions obtained from the state-of-the-art first-principles calculations of the electronic structure, phonon density of states, and reaction path will unravel how graphene can be used as a corrosion-resistant coating and guide further studies aimed at developing more efficient nanocoatings. © 2012 American Physical Society.