The perturbational method developed in the present paper is applied to the interaction between a polymer and a small molecule using a few simple model systems. The validity of our method is studied by comparing the results obtained with the perturbation method and the tight binding (SCF) crystal orbital method. The total electronic energies and charge distributions obtained are in good agreement with each other for the two methods. This result leads to the conclusion that the present perturbational approach is promising for application to interactions between real polymers and impurities.
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