Structure, vibrational spectra, dipole moment, and stability of gaseous licn and linc

An ab initio Hartree-Fock calculation of the structure of gaseous LiCN and LiNC has been performed using a basis set of 84 uncontracted and 45 contracted Gaussian atomic functions. The calculated Li-C distance is 3.6317 a.u.; the calculated C-N distance is 2.1915 a.u. for linear LiCN. For linear LiNC the calculated Li-N distance is 3.3354 a.u.; the calculated N-C distance is 2.1857 a.u. No experimental gasphase data have been reported, but the calculated C-N and N-C distances agree well with experimental C≡N bond lengths in other molecules. The calculated linear stretching mode frequencies are v 1≈2375, v2≈670 cm-1 (6Li 12C14N), and v1≈2367, v2≈785 cm-1 (6Li14N13C), agreeing with v1≈2250 cm-1 for other molecules. For linear 6Li14N12C, a bending mode frequency of ≈250 cm-1 was calculated. The predicted dipole moment is very high (3-4 a.u.). A marginal energy difference of 0.0141 a.u. between LiCN and LiNC was found, LiNC being the more stable.