Atomic structure and cohesion energy of isolated SiC clusters

The first-principle calculations of the atomic and electronic structures and cohesion energy of fullerene-like Si$_{60}$C$_{60}$ clusters have been carried out. A model of two-layer fullerene-like Si$_{12}$C$_{12}$@Si$_{48}$C$_{48}$ cluster with mixed $sp^2/sp^3$ bonds has been built for the first time. Ab initio calculations are performed in terms of the electron density functional and the hybrid B3LYP functional theory. The stability and the energy gap width of the clusters are estimated in the dependence on its geometry. It is shown that cohesion energy of two-layer fullerene-like Si$_{12}$C$_{12}$@Si$_{48}$C$_{48}$ cluster exceeds the cohesion energy of the other fullerene-like clusters with the same number of atoms, but is inferior to the SiC cluster with sphalerite structure. The relaxation of two-layer cluster is shift on outward the surface layer occurs.