Ab initio predictions for silicon analogs of astrophysically interesting molecules: SiC2H2, SiH2CN, SiH2C2, and CH2CSi

Ab initio geometries are reported for silicon analogs of the cyclopropenylidene ring, the cyanomethyl radical, and the vinylidenecarbene chain. The calculations employ fairly large basis sets, and, where appropriate, they are based on small multiconfiguration wave functions. The theoretical predictions should prove useful for laboratory and astronomical studies of these silicon-containing molecules.