Is 2-D Graphite an Ultimate Large Hydrocarbon? 1. Energy Spectra of Giant Polycyclic Aromatic Hydrocarbons

摘要

The energy spectra of three classes of polybenzenoid hydrocarbons with a large number N (N≈ 103) of carbon atoms have been studied theoretically. It is shown that in the asymptotic case N →∞ the energy gap (EG) △E(N→∞) is different from zero if the electron correlation is taken into account; that is, the Jr systems calculated should possess semiconductor properties. The results for the △E(N→∞) ≠ 0 of the hydrocarbons are in qualitative agreement with the results calculated for the EG of three classes of 1-D ladder polymers, which can be considered as models of quasi-l-D graphite. With increasing width (L) of the polymers, the band gap △E(L→∞) approaches a value different from zero. The problem of the existence of defect states of hydrocarbons with vacancies is briefly discussed.