Ab initio dynamic polarizabilities of polymers. I. Hydrogen chain models

Ab initio dynamic polarizabilities per unit cell of infinite stereoregular molecular hydrogen chains are calculated at the coupled Hartree-Fock level of approximation by using the random-phase approximation and the STO-3G and double-zeta atomic basis sets. Comparison with molecular calculations on increasingly large oligomeric chains emphasizes the nice extrapolation property of the polymeric technique that provides asymptotic values very close to the largest oligomeric values. The poles of the polarization propagator associated with the electric dipole polarizability correspond to the singlet excitation energies. Comparisons are performed with other techniques that provide the band gap.