Electronic Properties of Hexagonal Graphene Quantum Rings from TAO-DFT.

Area of Science:

• Computational Chemistry
• Materials Science
• Condensed Matter Physics

Background:

• Predicting electronic properties of graphene nanosystems is challenging for conventional methods like Kohn-Sham (KS) density functional theory (DFT).
• Strong static correlation effects in these systems hinder accurate conventional DFT calculations.
• Thermally Assisted Occupation (TAO) DFT is a novel method proposed to overcome these limitations.

Purpose of the Study:

• To utilize TAO-DFT for predicting the electronic properties of hexagonal graphene quantum rings (n-HGQRs).
• To investigate the ground state nature and electronic structure evolution of n-HGQRs with increasing system size.

Main Methods:

• Application of TAO-DFT to calculate electronic properties of n-HGQRs.
• Systematic investigation of n-HGQRs with n ranging from 3 to 15.
• Analysis of ground state spin states and TAO-orbital localization.

Main Results:

• TAO-DFT predicts singlet ground states for all investigated n-HGQRs (n=3-15).
• A transition from nonradical to polyradical character is observed as n-HGQR system size increases.
• The polyradical nature correlates with increased localization of active TAO-orbitals at the inner and outer edges of the rings.

Conclusions:

• TAO-DFT provides a reliable approach for studying the electronic properties of graphene quantum rings.
• The size-dependent transition to a polyradical state in n-HGQRs is a key characteristic.
• TAO-orbital localization is crucial for understanding the electronic behavior of these systems.