Determination of ab initio polarizabilities of polymers: Application to polyethylene and polysilane

An ab initio method for calculating the longitudinal linear polarizability of polymeric chains is described. This method is equivalent to an uncoupled Hartree–Fock scheme. It is applied to polyethylene and polysilane in minimal STO‐3G and extended 4‐31G basis sets. The study describes important techniques for solving the difficulties met in actual calculations: band reordering of the band structures, calculation of analytical derivatives of the energy bands ϵn(k) and LCAO coefficients cnp(k), and errors caused by the improper lattice sum truncations of the Hartree–Fock matrix.