BULK PROPERTIES FROM FINITE-CLUSTER CALCULATIONS .7. ACCURATE ABINITIO CALCULATIONS ON THE PEIERLS DISTORTIONS IN POLYACENE

Properties of both the undistorted and the Peierls-distorted polyacene polymers are obtained with the help of Pade approximants from the results of HF/6-311 G** and MP2/6-311 G** electronic structure calculations on the respective finite clusters. At the Hartree-Fock level, the (E)-distorted structure has the lowest energy per unit cell. At the correlated level, the undistorted structure is slightly favored. The C-C bond alteration is found to be more pronounced in the (Z)-distorted isomer than in the (E)-distorted one.