Fundamental gap of fluorographene by many-body GW and fixed-node diffusion Monte Carlo methods

Area of Science:

• Condensed Matter Physics
• Materials Science
• Computational Chemistry

Background:

• Fluorographene (FG) is a graphene derivative with potential applications due to its large bandgap.
• Existing theoretical predictions for FG's fundamental (Δ_f) and optical (Δ_opt) gaps show significant experimental discrepancies.
• Accurate band gap determination is crucial for understanding and utilizing FG's electronic properties.

Purpose of the Study:

• To establish a definitive benchmark for the fundamental gap (Δ_f) of fluorographene.
• To accurately calculate the exciton binding energy (E_b) in FG.
• To address and clarify potential misinterpretations of computational methods for solid-state band gaps.

Main Methods:

• Many-body GW calculations for electronic band structure.
• Fixed-node diffusion Monte Carlo (FNDMC) for accurate energy calculations.
• Bethe-Salpeter equation (BSE) to determine optical properties and exciton binding energy.

Main Results:

• A precise benchmark value for the fundamental gap of fluorographene: Δ_f ≈ 7.1 ± 0.1 eV.
• Calculated first exciton binding energy E_b = 1.92 eV.
• Identified conditions under which FNDMC with specific trial wave functions yields Δ_f rather than Δ_opt.

Conclusions:

• The study provides a highly accurate, benchmark value for the fundamental gap of fluorographene.
• The findings clarify the interpretation of computational results for solid-state band gaps, particularly concerning FNDMC.
• Accurate electronic properties of FG are established, aiding future research and applications.