The electronic band structure of polydiacetylenes with second- and third-neighbor hopping interaction

We have studied the energy band structure of polydiacetylenes (PDAs) using the extensional Hückel Hamiltonian that includes the nonnearest-neighbor hopping interactions. The results show that with increase in the nonnearest-neighbor hopping interaction parameters r1 and r2, (i) the energy band symmetry is broken and the energy gap 2D has changed, (ii) the locations and the widths of energy bands have changed and their shifts depend mainly on r1 (next-neighbor hopping interactions), and (iii) the energy gap 2D depends mainly on r2 (third-neighbor hopping interactions), the effects of the nonnearest-neighbor hopping interaction on the band structure are discussed.