Magnetic Property of Fullerene C20 : A First-Principles Study
Icuk Setiyawati1*, Yu-Hui Tang1
1Physics, National Central University, Jhong-Li, Taoyuan, Taiwan
* presenting author:ICUK SETIYAWATI,
Magnetic Property of Fullerene C20 : A First-Principles Study
Icuk Setiyawati1and Yu-HuiTang1*(唐毓慧)
1 Department of Physics, National Central University, Jhong-Li, Taiwan
From the production in the gas phase by Prinzbach[1], the C20 as the smallest fullerene has been attracted considerable attention among scientists. In the following year, Wang et al[2]sucessfully synthesized the solid phase of C20 using ion beam irradiation method and found that the fullerene C20 behave as the building block of hexagonal crystal. What more interesting is the existence of magnetism in carbon materials is experimentally investigated, i.e chains of interacting radicals, carboneous substances with mixture sp2 and sp3 coordinated atoms, nanographite, nanodiamond, carbon nanofoams, etc. This evidence supports the theoretical predictions that electronic instabilities in pure carbon may give rise to ferromagnetic even at room temperature[3].
To investigate the underlying mechanism of the magnetism of fullerene C20 cage structure, we employed the density functional theory (DFT) within the nonequilibrium Keldysh Green’s function (NEGF) formalism to study the spin-polarized density of states of the isolated nonmagnetic C60 and C20 bowl-like molecules, which are truncated by the mixture of pentagons and hexagons as shown in Figs. 1(a) and (b), and of the isolated magnetic C20 cage and C15 bowl-like molecules, which exhibit purely pentagon-bunching structure as shown in Figs. 1(c) and (d). For the C15 bowl-like structures, the spin-polarized molecular levels are mainly contributed by those C atoms on the zigzag edge, while, for the C20 cage structure, all molecular levels are spin-polarized resulting from the zigzag boundaries between pentagons which is also verified by VASP calculation. Such zigzag-boundary induced magnetic properties of C20 cage and C15 bowl-like molecule can be analog to the graphene nanoribbon with zigzag edges [4]. Moreover, the non-magnetic and insulating properties of C60 and C20 bowl-like molecules can be attributed to the mixture of zigzag and armchair boundaries between hexagon and pentagons.
The structural stability of C20 cage structure is investigated by performing the phonon vibrational modes calculation, and the spin-polarized property of another possible stable structure is reinvestigated. (Contract No. NSC 102-2112-M-008-004-MY3)
[1] H. Prinzbach et al., Nature (London) 407, 60 (2000).
[2] Z. Wang et al., Phys. Rev. Lett A 280, 351-356 (2001).
[3] M. Tatiana (Magnetism of Carbon-Based Materials).,Studies of High-Tc Superconductivity, vol.44-45 edited by A. Narlikar (2001).
[4] K. Nakada et al., Phys. Rev. B 54,17954-17961 (1996).

Keywords: Fullerene, C20 , spin-polarized , density of states, phonon