Ab initio study of silicon-multisubstituted neutral and charged fullerenes -: art. no. 085411

The electronic and structural properties of Si-doped fullerenes, obtained from C-60 by replacing up to 12 C atoms with Si atoms, are studied by means of first-principles density-functional theory calculations using numerical atomic orbitals as basis sets. We have analyzed the relative stability of several C60-xSix isomers, with x=1, 2, 3, 6, and 12. We find that, for x=3 and 6, the Si atoms strongly "prefer'' to be first neighbors of each other, in order to minimize the number of SI-C bonds. However, these configurations of lower energy present a few relatively weak Si-C and Si-Si bonds that could indicate possible breaking paths. For a better comparison with the experimental measurements, we have also considered some positively charged ions, and report the differences between properties of these ions and the corresponding neutral molecules.