Density-functional study for the oligomers of poly(para-phenylene):: Band structures and dielectric tensors

The electronic and optical properties of the oligomers of poly(para-phenylene) (PPP) in their crystalline phases are calculated. In particular, the 2-, 3-, 4-, and the technically most important 6-unit oligomer para-hexaphenylene (6P) are considered. The electronic band structures are compared with the corresponding molecular orbitals in isolated molecules and the effect of intermolecular interactions is discussed. Connections between previous studies on the band structure of three-dimensional PPP and the present work are established. From the quasiparticle band structures the dielectric tensors are calculated and discussed also with respect to the corresponding transitions in the isolated molecules.