Is 2-D graphite an ultimate large hydrocarbon? II. Structure and energy spectra of polycyclic aromatic hydrocarbons with defects

The structure and energy spectra of four classes of polybenzenoid hydrocarb ons with different edge structures, a large number N (N similar to 10(4)) o f carbon atoms, and different types of defect states (Tamm, Schottky and ch emisorption states) have been studied theoretically. Several types of (prob ably) stable monoradicals and triplet biradicals with singly occupied MOs i n the energy gap (molecular analogues of semiconductors with defect states) are characterized which could be used in the molecular electronics. A new concept for viewing high-spin pi systems with ferromagnetically coupled ele ctrons within the half-filled band of NBMOs in term of point defects (vacan cies) was developed. The NBMOs can be considered as surface states (Tamm or Schottky).