First-Principles Study on the Magnetism of Triangular Graphene Quantum Dot with Armchair Edges Decorated by Zigzag Extensions

Abstract

Using first-principles calculations, we investigate the effect of zigzag extensions on the magnetic properties of triangular graphene quantum dot with armchair edges. The results show that when two or three zigzag extensions are added to the armchair edges of triangular graphene quantum dot, the ground states of most modified structures conform to the Lieb’s theorem, while some structures violate the Lieb’s theorem, which can be attributed to the small energy difference be-tween the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). In addition, we find that the ground states of partial modified structures remain in the low-spin state, while the others change from a low-spin state to a high-spin state. Our findings have important implications for manipulating the magnetism of graphene quantum dot with arm-chair edges.