Formation of SiC Clusters with Bucky Diamond Structures*

SiC clusters with bucky diamond structures have been found in a quantum-mechanical molecular dynamics study based on our recently developed self-consistent and environment dependent Hamiltonian in the framework of a linear combination of atomic orbitals [1]. Starting from a spherically truncated bulk diamond structure, stable structures of SiC clusters containing 147 atoms were studied for various compositions of Si and C atoms. In particular, the following initial configurations were considered: (i) C-rich configuration with Si-core, (ii) Si-rich configuration with C-core, and (iii) an almost equal admixture Si and C atoms. It is found that in the first case Si atoms are dragged to the exterior and a cage-like structure formed, while in the second case some C atoms remain in the interior region and some move to the exterior region forming distorted tetrahedral structures with Si atoms. Finally, in the third case, the bucky-diamond structure is obtained, where the interior has a diamond-like structure and the exterior a fullerene-like structure. The reason why (SiC)$_{147}$ clusters form different stable structures can be understood based on hybridization characteristics of Si (\textit{sp}$^{3 })$ and C atoms (\textit{sp}$^{1}$, \textit{sp}$^{2}$, and \textit{sp}$^{3 })$, respectively. [1] Leahy \textit{et al}. Phys. Rev. B74, 155408 (2006).