Molecular orbital calculations of electric field gradients at halogen nuclei in solid chlorine and bromine

Abstract

Using the MO LCAO method in CNDO and INDO approximations, calculations of the electronic structure of polyatomic clusters in solid Cl 2 and Br 2 have been performed. The energies of the molecular orbitals of the clusters are compared with the available experimental data and theoretical results. The effect of d-orbitals on intermolecular bonding is examined in the case of solid chlorine, and the parameters of the electric field gradient tensor at halogen nuclei are evaluated in both cases of solid chlorine and bromine. The calculated quadrupole coupling constants are in satisfactory agreement with the observed values, but the electric field gradient asymmetry parameter is found to be very small in every case, in contradiction of the experimental results. Finally, the possible reasons for such a discrepancy are discussed.