The physics of single-side fluorination of graphene: DFT and DFT + U studies

Abstract

We present density functional theory (DFT) calculations of the electronic and magnetic properties of fluorine adatoms on a single side of a graphene monolayer. By extrapolating the results, the binding energy of a single fluorine adatom on graphene in the dilute limit is calculated. Our results confirm that the finite-size error in the binding energy scales inversely with the cube of the linear size of the simulation cell. We establish relationships between stability and C-F bond nature, diffusion of fluorine adatoms and total magnetization in different configurations of adatoms. For single-side fluorination, sp 2.33 is the maximum p-content rehybridization found in the C-F bond. We show that semilocal DFT cannot predict correctly the magnetic properties of fluorinated graphene and a higher level theory, such as DFT+U is needed. The results indicate a tendency of graphene to reduce the imbalance between adsorption on the two sublattices, and therefore total magnetization, through low-energy-barrier pathways on a time scale of ~10 ps at room temperature. The thermodynamically favored arrangements are those with the smallest total magnetization. Indeed, the electronic structure is intimately related to the magnetic properties and changes from semi-metallic to p-type half-metallic or semiconducting features, depending on the adatoms arrangement.

Recent Advances in Fluorinated Graphene from Synthesis to Applications: Critical Review on Functional Chemistry and Structure Engineering

“…The fluorine content is the simplest and fundamental character of FG, which has been introduced in the above intrinsic properties section. [94,104,122,123,128,130,236] Herein, we mainly aim at the recent processes about the engineering of other structural characters such as fluorine distribution, fluorine type, radicals, interlayer structure, and present how do the corresponding performances and applications be regulated and optimized.…”

Fluorographene and Its Composites: Fundamentals, Electrophysical Properties, DFT Studies, and Advanced Applications

“…Further, Marsusi et al studied F adatoms' stability, dynamics, magnetic behavior, and electronic structure on graphene by DFT and DFT-U calculations. [52] Their study showed that i) the formation energy of single-sided FG is favorable than hydrogenated graphene revealed FG is more stable at a higher temperature, ii) the bond nature of C-F was found to be semi-ionic in nature for low concentrations of fluorine, which implies specific features of FG such as smaller diffusion barriers, than hydrogenated graphene, and iii) the magnetic moment and electronic structure of FG was show p-type half-metallic or semiconducting features (depending on the adatom arrangements at a given concentration) studied by a DFT+U. Further, this study was extended by Langer et al, where the stability of F ad-atom on graphene and the reactivity of C-F has been evaluated.…”

Halogen Functionalization in the 2D Material Flatland: Strategies, Properties, and Applications

“…However, the single‐side half‐fluorinated graphene (CF 0.5 ) is a zero‐gap metal because of the exchange splitting of the dangling C π‐orbitals coupled with the impure states of F. Density functional theory (DFT) calculations [ 108 ] predicted that the chair configuration of CF is more stable than the zigzag, boat, and armchair configurations, and they exhibited a varying bandgap of 3.20–4.23 eV within the GGA approximation. Spin‐polarized DFT+U [ 112 ] and DFT [ 113,114 ] calculations showed that the diffusion of F adatoms on graphene reduced the thermodynamic imbalance of the sublattices, and increasing the fluorination degree changed the fluorinated graphene from a p‐type half‐metal to a semiconductor.…”