Ab Initio Investigation of Structures and Stability of SinCm Clusters

Abstract

Various structural possibilities for Si n C and Si n C 2 (n = 1-7) neutral and anionic isomers were investigated using the second-order Miller-Plesset (MP2) approximation at the 6-311+G(d) level. The calculations predicted the existence of a number of previously unknown isomers (i.e., Si 5 C 2 and Si 6 C 2 ). We found that the basis set [6-31G(d)] with the MP2 approximation was too small to explain the photoelectron spectra of Si n C m clusters reasonably. Our present results agree satisfactorily with the photoelectron spectroscopy. The strong C-C bond is no longer the dominant factor in the building-up principle of mixed Si 6 C 2 neutral and anionic clusters. The calculated adiabatic electron affinities in their ground states showed that Si n C m (n + m = 3, 6) clusters are more stable than any others in Si n C and Si n C 2 (n = 1-7) species, being consistent with the observed TOF signal intensities. Their stability tends to decrease with the increase in the size of these clusters.