Permeation of Low-Z Atoms through Carbon Sheets: Density Functional Theory Study on Energy Barriers and Deformation Effects

TL;DR

This study uses density functional theory to analyze how low-Z atoms permeate through graphene sheets, examining energy barriers and deformation effects across different atoms and interaction regimes, with implications for fusion materials.

Contribution

It provides a comprehensive DFT analysis of low-Z atom permeation through graphene and hydrogenated graphene, including energy barriers and deformation effects, expanding understanding of permeation mechanisms.

Findings

Energy barriers range from 5 eV for H to 20 eV for Ne.

Chemical bonding facilitates permeation for O, C, B, and Be.

Results align with experimental and theoretical data, informing fusion material modeling.

Abstract

Energetic and geometric aspects of the permeation of low-Z atoms through graphene sheets are investigated. Energy barriers and deformations are calculated via density functional theory for the permeation of H, He, Li and Be atoms at several surface sites and at a hollow site for atoms B, C, O and Ne atoms. Graphene is modeled by large planar polycyclic aromatic hydrocarbons and the convergence of both energy barriers and deformation curves with increasing size of these hydrocarbons is investigated. Effective energy curves are summarized for the atoms under consideration in three different interaction regimes realized different geometrical constraints. In addition to the bare graphene model, the interaction between low-Z atoms and 100% hydrogenated coronene as a model for graphane is also investigated. The adiabatic barriers range from about 5 eV (1 eV = 1.602 x 10-19 J) for H to about 20 eV for Ne. Facilitation of the permeation by temporary chemical bonding is observed for O and C and for B and Be when interacting with hydrogenated coronene. The results are in good agreement with existing experimental and theoretical work and reflect the essential physics of the dynamics of H bombardment of graphite (0001) surfaces. Implications for modeling chemical sputtering of graphite in a mixed-material scenario as it will be the case in the next step fusion experiment ITER and potential building are discussed.