Theoretical study on the structures, isomerization and stability of SiC4 isomers

The structures, energetics, dipole moments, vibrational spectra, rotational constants, and isomerization of singlet SiC4 isomers were explored using ab initio methods. Five types of isomers, a total of 11 minima, connected by 11 interconversion transition states, were located on the potential energy surface at the MP2/6-311G(d, p) level. More accurate energies were obtained at the G3(MP2) level. With the highest isomerization barrier, a C2v tetra-angular cone possesses the largest kinetic stability. The lowest-lying structure, linear SiCCCC is also highly kinetically stabilized. Besides, D2d bicyclic c-Si(CC)(2), C2v five-membered ring c-SiCCCC, another C2v tetra-angular cone isomer and C3v trigonal bipyramid isomer are also considered to be kinetically stable, because their isomerization barriers are all over 10 kcal/mol. Other isomers cannot be kinetically stabilized with considerably low isomerization barriers. Investigation on the vibrational spectra, dipole moments, and rotational constants for SiC4 isomers are valuable for their detections in the interstellar space and laboratory.