Stabilizing the silicon fullerene Si20 by thorium encapsulation -: art. no. 115429

We show using ab initio electronic structure calculations that the dodecahedral fullerene of silicon 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 sp(3) bonding in silicon makes it an optimal cage with all pentagonal faces in contrast to carbon for which C-20 is difficult to stabilize. Similar to 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.