High-symmetry high-stability silicon fullerenes: A first-principles study

It is shown by ab initio calculations that very stable high-symmetry fullerenes of the form ${\mathrm{Si}}_n{\mathrm{H}}_n$, $n=20$, 28, 30, 36, 50, and 60, can be formed with large energy gaps suitable for optoelectronic and other applications. Quantum confinement seems to be violated if one neglects the essentially two-dimensional nature of the electron gas. Comparison with similar carbon fullerenes, such as ${\mathrm{C}}_{20}{\mathrm{H}}_{20}$ and ${\mathrm{C}}_{60}{\mathrm{H}}_{60}$, reveals full similarity in their electronic and geometrical structures, which is suggestive of possible routes for their synthesis. These silicon fullerenes constitute the best manifestation of carbon and silicon homology.

Figure 1

(Color online) The high-symmetry high-stability structures of ${\mathrm{Si}}_n{\mathrm{H}}_n$, $n=4,\dots ,60$ cages.

Figure 2

(Color online) Charge density (top), HOMO (in the middle), and LUMO (bottom) orbitals of ${\mathrm{C}}_{20}{\mathrm{H}}_{20}$ (left) and ${\mathrm{Si}}_{20}{\mathrm{H}}_{20}$ (right) fullerenes.

Figure 3

(Color online) Binding energy per silicon atom and HOMO-LUMO and optical gaps as a function of silicon (or hydrogen) atoms.