Theoretical Study on Structural Stability of Alloy Cages: a Case of Silicon-doped Heterofullerenes

Structural stability and Si-substitution pattern in fullerene cage of C 60-n Si n are thoroughly investigated by integrating density functional calculations with a colorbond graph (CBG) model.We find that the parameterized CBG model with genetic algorithms can efficiently scan the large configuration space of alloy and therefore identify the low-energy region within the first-principles accuracy.Low-energy (stable) structures of C 60-n Si n in carbon-rich region (1 ≤ n ≤ 30) were identified and the silicon atoms are found to tend to aggregate in the fullerene cage.The mixing energy of these low-energy structures is ∼ 35 meV/atom and insensitive to the Si concentration.We expect that these alloy fullerene cages can be synthesized experimentally at elevated temperatures.