A Molecular Orbital Theory of Polymers

Abstract

<p>The molecular orbital method and the underlying approximations are reviewed. A molecular orbital method appropriate to the study of polymers is then developed in the Complete Neglect of Differential Overlap approximation. The resulting equations, which are discussed in some detail, are used to study a number of real and model polymers which have regular structures. The model systems are chosen to represent a wide range of physical characteristics. A discussion of the results of these calculations which show that the method gives physically responsible results is presented. Some problems specific to the theory of polymers are identified, discussed, and, in a number of cases, resolved.</p> <p>The limitations on the method imposed by the assumption that the structure of the polymer is regular are discussed. A method, based on self-consistent perturbation theory, is proposed which permits the calculation of the effects of small irregularities on the electronic structure of polymers. The characteristics of the method are discussed using an examples calculations on small molecules. A formalism appropriate to the study of polymers is then developed. Model calculations on a chain of hydrogen molecules are used to demonstrate the effectiveness and potential uses of the method. The linear chain of equally-spaced hydrogen molecules is shown to be stable with respect to distortions along the axis of the chain.</p>