The self-consistent charge density functional tight-binding (DFTB) theory study of carbon adatoms using tuned Hubbard U parameters

TL;DR

This study employs self-consistent charge DFTB with tuned Hubbard U parameters to analyze the electronic structure of C61, demonstrating improved accuracy in orbital energies and HOMO-LUMO gaps for carbon adatom systems.

Contribution

It introduces a methodology for tuning Hubbard U in DFTB to better model electronic properties of carbon adatoms on fullerene C60.

Findings

Tuned Hubbard U reduces localized orbital energies.

Improves HOMO-LUMO gap accuracy.

Provides a reference for future carbon material studies.

Abstract

The self-consistent charge density functional tight-binding (DFTB) theory is a useful tool for realizing the electronic structures of large molecular complex systems. In this study, we analyze the electronic structure of C61, formed by fullerene C60 with a carbon adatom, using the fully localized limit and pseudo self-interaction correction methods of DFTB to adjust the Hubbard U parameter (DFTB+U). The results show that both the methods used to adjust U can significantly reduce the molecular orbital energy of occupied states localized on the defect carbon atom and improve the gap between highest occupied molecular orbital(HOMO) and lowest unoccupied molecular orbital(LUMO) of C61. This work will provide a methodological reference point for future DFTB calculations of the electronic structures of carbon materials.