Absence of stable atomic structure in fluorinated graphene

TL;DR

This study uses first-principles calculations to show that fluorination causes distortions in graphene, leading to metastable patterns and increased fluorine mobility, which impacts the material's magnetic and structural properties.

Contribution

It reveals the absence of stable atomic structures in fluorinated graphene and details how fluorine migration and pattern formation occur.

Findings

Metastable fluorination patterns are energetically favored.

Fluorine migration barriers decrease with higher fluorine content.

Increased fluorine adatoms may induce magnetic moments.

Abstract

Based on the results of first-principles calculations we demonstrate that significant distortion of graphene sheets caused by adsorption of fluorine atoms leads to the formation of metastable patterns for which the next step of fluorination is considerably less energetically favorable. Existence of these stable patterns oriented along the armchair direction makes possible the synthesis of various CFx structures. The combination of strong distortion of the nonfluorinated graphene sheet with the doping caused by the polar nature of C-F bonds reduces the energy cost of migration and the energy of migration barriers, making possible the migration of fluorine atoms on the graphene surface as well as transformation of the shapes of fluorinated areas. The decreasing energy cost of migration with increasing fluorine content also leads to increasing numbers of single fluorine adatoms, which could be the source of magnetic moments.