“Impurity” induced localized hole states of a one dimensional linear chain: Magnus green salt

The effect of an interstitial (off chain) negative halide ion on the one dimensional molecular orbital or “tight binding” states of a 20 site metal ion linear chain is examined. It is assumed that the halide ion shifts the chain site potentials an amount given by the Coulomb potential resulting from a negative point charge placed at the halide ion site. The eigenvalues and eigenvectors of the 20 site problem have been obtained numerically. For an initially unperturbed metal 5dz2 bandwidth of 1 eV and a background dielectric constant ε=1, the binding energy of a 5dz2 hole is found to be 0.46 eV. This value is in good agreement with twice the observed conductivity activation energy, ? 0.6 eV, in extrinsic samples of the linear chain platinum compound Magnus's green salt. The general dependence of the eigenvalues and eigenvectors will also be presented as a function of bandwidth and background dielectric constant. © 1975, American Institute of Physics. All rights reserved.