Electronic States of Heavily Doped Molecular Crystals—Naphthalene. I. Theoretical

Abstract

The energy spectrum of heavily doped molecular crystals was treated in the Green's function formulation. The mixed-crystal Green's function was obtained by averaging over all possible impurity distributions. The resulting Green's function, which takes the form of an infinite perturbation expansion, was further approximated by a closed form suitable for numerical calculations. The density-of-states functions and optical spectra for binary mixtures of normal naphthalene and"'deuterated~naphthalene were calculated using the pure-crystal density-of-states functions. The results showed that when the trap depth is large two separate energy bands persist, but when the trap depth is small only a single band exists. Furthermore, in the former case it was found that the intensities of the outer Davydov bands are enhanced whereas the inner bands are weakened. Comparisons with previous theoretical calculations and expetimental results are also made.

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