DFT screened-exchange approach for investigating electronical properties of graphene-related materials

TL;DR

This paper uses a screened-exchange DFT method to accurately calculate the electronic properties of graphene and nanoribbons, showing improved agreement with experiments and significant effects on bandgaps and spin-polarization.

Contribution

It introduces the sX-LDA approach for graphene materials, providing more accurate electronic structure predictions than traditional LDA or GGA methods.

Findings

Bandstructure renormalization aligns with experimental data.

Band gaps in nanoribbons increase by over 200%.

Non-local exchange significantly affects spin-polarization.

Abstract

We present ab initio calculations of the bandstructure of graphene and of short zigzag graphene nanoribbons by the screened-exchange-LDA method (sX-LDA) within the framework of density functional theory (DFT). The inclusion of non-local electron-electron interactions in this approach results in a renormalization of the electronic bandstructure and the Fermi velocity compared to calculations within local density approximation (LDA) gives good agreement with experiment. Similarly, the band gaps in zigzag nanoribbons (ZGNR) are widened by more than 200%, being of similar magnitude than bandgaps from past studies based on quasiparticle bandstructures. We found a noticeable effect of non-local exchange on the spin-polarization of the electronic ground state of ZGNRs, compared to LDA and GGA-PW91 calculations.