Abstract
Silicon carbide (SiC) is technologically a significant material. A recent report on the abundance of C60 fullerenes in interstellar space, along with the presence of the SiC precursors, sparked interest in potentially similar SiC nanostructures. The C60 fullerene was found experimentally and is an exceptionally stable form of carbon. As Si and C have similar valence electron properties, it has been long envisioned that Si and SiC could also form similar fullerene type structures. In this paper, Si30C30 fullerene-derived clusters were studied from the first principle starting from an ideal Si60 fullerene templet with various arrangements of silicon and carbon atoms, and then relax them without any symmetry constraint. Hydrogen passivation was considered as well to model the effect of ligands that may be available during the chemical synthesis processes. We have found that after passivation, the relative stability of different configurations of Si30C30 clusters changed compared to the unpassivated structures, while some structures collapsed. We have also noticed several Si-Si and Si-C double bonds in the unpassivated structures. Upon relaxation, some Si atoms lost their hydrogen, while carbon atoms capture those hydrogen atoms. Finally, we tested the endohedral doping of a transition metal, tungsten atom, to stabilize and magnetize Si30C30. With hydrogen passivation, the magnetic moment on W atom was enhanced. Overall, the effects of passivation on these fullerene structures are not very straightforward.
Highlights
Due to the similar valence electronic structures of Si and C, there are reports on silicon fullerene being similar to C60 fullerene
We have considered Si30C30 clusters with various arrangements of silicon and carbon atoms, starting from a Si60 fullerene structure with icosahedral symmetry and relaxing those configurations without any symmetry constraint
This is the only structure in this study that was relaxed with symmetry constraints
Summary
Due to the similar valence electronic structures of Si and C, there are reports on silicon fullerene being similar to C60 fullerene. A recent study showed that, for Si60, a lower energy structure could be achieved by a triangular-shaped structure with three Si20 units at the vertices (Bainglass et al, 2017) rather than by a hollow cage structure. Cage-like clusters are desirable because the hollow of the cage can be used for endohedral doping. Several endohedral dopants in the Si cages were considered to stabilize fullerene-like structures and to produce materials with tailored properties (Hiura et al, 2001; Kumar and Kawazoe, 2001). Some of these endohedral transition-metal-doped nanostructures can exhibit magnetic properties as well
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