G. Froudakis et al., A COMPARATIVE AB-INITIO STUDY OF THE SI2C4, SI3C3, AND SI4C2 CLUSTERS, The Journal of chemical physics, 101(8), 1994, pp. 6790-6799
Various structural possibilities for the Si2C4 and Si4C2 clusters are
investigated by employing a basis set of triple-zeta plus polarization
quality; electron correlation is generally accounted for by second-or
der Moller-Plesset and, in certain instances, by higher-order perturba
tion (CASPT2) approaches. The building-up principle recently suggested
from an analysis of Si3C3 clusters is found to be fully operative for
Si2C4 and Si4C2 clusters. A comparison of the structure and stability
of various geometrical arrangements in the series C-6, Si2C4, Si3C3,
Si4C2, and Si-6 shows that linear and planar structures become rapidly
less stable if carbons are replaced by silicons and that the three-di
mensional bipyramidal forms become less favorable as soon as silicons
are exchanged by carbons in the parent Si-6 structure. The effects can
be rationalized in qualitative terms based on differences in silicon
and carbon bonding.