Stability of carbon-doped silicon clusters: FP-LMTO molecular dynamics calculations

Using full-potential linear-muffin-tin-orbital molecular-dynamics (FP-LMTO-MD) method, we have investigated the effect of carbon heteroatom on the geometric structures and stability of Sin (n = 2-19) clusters systematically. It has been found that one C atom does not change the geometrical configurations of the pure Sin clusters even though they undergo serious distortion, especially, for the smaller Si clusters. As the atom number increases, the influence of the C impurity atom would decrease. The C atom usually locates at the sites with more than three coordination in the most stable structures for the larger neutral Sin−1C clusters (n ≧ 6). It improves some bond strength, which increases the stability of some carbon-doped silicon clusters. On the other hand, the C heteroatom probably reverses the energy orderings of the Si clusters with small difference. Furthermore, their ionic geometric structures have been also investigated. Similarly, addition or removal of an electron does not change the geometrical configurations compared with those of their corresponding neutral clusters, but their energy orderings probably change.