双链DNA电子结构与光学跃迁吸收谱研究

In this paper，based on the tight-binding model, we calculate the energy band structure, electron density and optical transitions absorption spectrum with two different base components of DNA sequences. By considering the influence of disorder in the base energies, we also analysis and compare the electron density and the optical transitions absorption spectrum of both DNA sequences. The results show that the electronic band structure of the poly (G)-poly(C) DNA and poly(A)-poly(T) DNA turn out the indirect band gap semiconducting electronic structure behavior. The band gap gradually disappears and the energy region broadens with the increasing of the magnitude of disorder. The parallel polarization absorption peak sites of the poly(G)-poly(C) DNA and poly(A)-poly(T) DNA are 1.87and 0.76 respectively, while the perpendicular polarization absorption edges of poly(G)-poly(C) DNA and poly(A)-poly(T) DNA are 1.84 and 0.68 respectively. In both low-energy and high-energy range, there exist perpendicular polarization absorption peaks. And there exist competition effect between the perpendicular and parallel polarization. With increasing of the disorder, both parallel polarization and perpendicular polarization absorption spectrum broadens. However, the phenomenon that poly(A)-poly(T) DNA change more significantly than the poly(G)-poly(C) DNA in the low energy region is revealed. As for the perpendicular polarization absorption spectrum, the peak in high energy region disappears with the increasing of disorder while the one in low energy region exhibits more tendency towards to lower frequency for poly(G)-poly(C) DNA.