Electronic properties of ppp-oligomers investigated from first-principles

We have performed first-principles calculations for crystalline oligomers of poly(para-phenylene) in the framework of density functional theory. The band structure of the 2-, 3-and 4-unit oligomer is determined. The band gap as a function of chain length excellently reproduces the experimental findings. Additionally we have studied the effects when generalized gradient corrections (GGA) are applied instead of the local-density approximation (LDA) for exchangeand correlation effects.