Magnetism of Edge Modified Nano-graphene

The multiple spin states of zigzag edge modified graphene molecules were analyzed to study the possibility of carbon based magnetic materials by using first principles density functional theory to select suitable elements for modification. Radical carbon modified C64H17 and dihydrogenated carbon C64H27 demonstrated that the highest spin state is most stable, which arises from the tetrahedral molecular orbital configuration in two up-spins at the zigzag edge. In contrast, oxygen modified C59O5H17 exhibited the lowest spin state to be most stable due to the cancellation of four spins at the oxygen site. Boron modified C59B5H22 had no π-orbit at the boron site, which meant the lowest spin state was most stable, whereas, C59N5H22 had two π-electrons, where spins cancelled each other out to yield the lowest stable spin state. Silicon modified C59Si5H27 and phosphorous modified C59P5H22 had a curved molecular geometry due to large atom insertion at the zigzag site, which also brought about a complex spin distribution. Radical carbon and dihydrogenated carbon modification were identified as promising candidates for designing carbon based magnetic materials.