Charge transfer in homogeneous chain with a defect

Based on the semi-classical Holstein Hamiltonian we consider charge transfer along a DNA chain. Recently it has been shown that the charge distribution in homogeneous chains in thermodynamic equilibrium depends not only on the temperature, but also on the length of the chain. We have studied numerically the case of DNA fragments consisting of adenines with a defect site in the middle of the chain. The results demonstrate qualitatively similar behavior of thermodynamic equilibrium quantities in the case of homogeneous chain and of the chain with a defect. Insertion of a trap-site enhances the stability of polaron states.