Structure and Thermal Stability of Co- and Fe-Intercalated Double Graphene Layers

We theoretically investigated arrangement of Fe and Co atoms between two graphene planes. We showed that below 690 K Co atoms form stable lattices—hexagonal (with the lattice parameters a = 0.354 nm and c = 0.406 nm) and cubic (with the lattice parameter of 0.244 nm), whereas Fe atoms form cubic lattice only (with the lattice parameter of 0.281 nm). The system intercalated with Co atoms is stable enough at high temperatures up to 740 K, while the Fe/graphene system is stable only at ∼550–600 K. We also demonstrated that the basic distance between the graphene planes (0.342 nm) increases to 0.566 nm for Fe intercalation and to 0.567 nm for Co intercalation.