Electronic Structures of Linear Polymers. II. Formulation and CNDO/2 Calculation for Polyethylene and Poly(tetrafluoroethylene)

Abstract

The Hartree–Fock procedure for infinite linear polymers is formulated by the use of the cyclic boundary condition. An actual calculation using this procedure is carried out for the various conformations of infinite polyethylene and poly(tetrafluoroethylene) in the semiempirical CNDO/2 SCF approximation. Polyethylene has an energy minimum at the C–C rotational angle $\text{ω\hspace{0.17em}=\hspace{0.17em}180°}$ or for the trans zigzag conformation, while poly (tetrafluoroethylene) has a minimum around $\text{ω\hspace{0.17em}=\hspace{0.17em}162°}$ , a slightly twisted trans zigzag conformation. Both are in excellent agreement with experimental results for the single crystals. Both polymers, experimentally good electric insulators, are calculated to have a large energy gap between the highest‐filled and the lowest‐vacant band. The segmental and atomic energy contributions and charge distributions are discussed in detail in comparison with alkanes and as functions of the conformational angle $\omega$ .