Abstract:

Using ab initio molecular orbital theory at the SOCI/MCSCF/HF/DH+d level, the equilibrium geometries, total energies, harmonic vibrational frequencies, zerro point vibrational energy and potential energy curves of the ground state and 8 excited states of Si_2 molecule were obtained. The relationship between the bond length and the electronic codriguration of the state was discussed. The results revealed that bond length and the harmonic vibrational frequency of the molecule strongly depended upon the number of π-electrons in the bonding MO's. The reported states ~3Π_g, ~5Σ~-_u, ~3Δ_u, ~3Σ~-_u have not been seen in literatures.

Key words: Si2, Ab initio calculation, SOCI, MCSCF, Excited state