Structures and energies of SimCn clusters (m = 2 - 6, n = 1 - m) have been investigated systematically at MP2/6-311G(d) level of theory. Several stable structures of Si6Cn are predicted for the first time. All the structures show that carbon atoms prefer forming kernels at the center of framework, surrounded by silicon atoms with small coordination number. The strong C-C bond favored over Si-C bond determines the structure of SimCn clusters. The binding energies show that the systems with the ratio of Si:C=1: 1 have the larger stability compared to the Si-rich hetero systems. (c) 2006 Elsevier B.V. All rights reserved.