Stabilizing the silicon fullereneSi20by thorium encapsulation

Abstract

We show using ab initio electronic structure calculations that the dodecahedral fullerene of silicon ${\mathrm{Si}}_{20}$ is stabilized by thorium encapsulation. Thorium is found to be the only element in the Periodic Table that stabilizes this fullerene with icosahedral symmetry in the neutral state. The preference for $s{p}^{3}$ bonding in silicon makes it an optimal cage with all pentagonal faces in contrast to carbon for which ${\mathrm{C}}_{20}$ is difficult to stabilize. Similar to ${\mathrm{C}}_{60}$, this is the highest symmetry cluster of silicon and should be abundant. It could lead to the possibilities of novel new phases and derivatives of silicon.