NEW IMPLEMENTATION OF A PROGRAM TO CALCULATE CORRELATED BAND STRUCTURES OF POLYMERS - AN APPLICATION TO THE BAND-STRUCTURE OF POLYPARAPHENYLENE (PPP)

A new program has recently been implemented with the aim of extending quasi-particle (QP) band structure calculations to polymers with large r unit cells. The theoretical background is briefly reviewed and the n ew algorithm described, which has been optimized for machines with vec tor processors. To illustrate the usefulness of this technique, calcul ations have been performed on polyparaphenylene (PPP) using a double-z eta basis set. The calculated QP band gap between the valence and cond uction bands is 2.3 eV, which compares favorably with the experimental value of 2.8 eV. The self-consistent field (SCF) result with the same double-zeta basis set is 8.7 eV. (C) 1994 by John Wiley and Sons, Inc .