Competition between structural distortion and magnetic moment formation in fullerene C${}_{20}$

Abstract

We investigated the effect of on-site Coulomb interactions on the structural and magnetic ground state of the fullerene C${}_{20}$ based on density-functional-theory calculations within the local density approximation plus on-site Coulomb corrections (LDA+$U$). The total energies of the high symmetry ($I_h$) and distorted ($D_{3d}$) structures of C${}_{20}$ were calculated for different spin configurations. The ground state configurations were found to depend on the forms of exchange-correlation potentials and the on-site Coulomb interaction parameter $U$, reflecting the subtle nature of the competition between Jahn-Teller distortion and magnetic instability in fullerene C${}_{20}$. While the non-magnetic state of the distorted $D_{3d}$ structure is robust for small $U$, a magnetic ground state of the undistorted $I_h$ structure emerges for $U$ larger than 4 eV when the LDA exchange-correlation potential is employed.

4 figures, 1 table