The geometric and electronic structures of I3− and I5− from effective-potential calculations (original) (raw)

1978, Journal of Molecular Structure

The (ab initio) effective-potential theory developed by Ewig et al. is applied to the structures of the polyiodide ions, &-and I,, The bare ions I,-and I,-are found by optimization of the geometry to be symmetric and linear. The counterion environment, however, greatly influences the equilibrium structure_ A symmetric, flexible counterion environment produces only a slightly altered symmetric, linear equilibrium structure for the I,-anion; whereas an asymmetric, rigid counterion frame leads to unequal bond lengths and bending of the anion. For the I,-anion, the potential energy calculated for bending of the central I-I-I angle, 01, is very small so that a slight interaction with the lattice will readily lead to the experimental bent structure with (Y = 94". At this value of cr, the two outer angles are found to be equal and close to the experimental value. The electronic structures of the Q-and I,-ions are also discussed_