Charge Carrier Mobilities in Periodic DNA Models

The drift mobility of electrons and holes has been calculated for various periodic DNA models using LCAO crystal orbitals and applying the variational method of transport theory. Since the energy bands are narrow, inelastic electron‐acoustic phonon scattering has been taken into account for all states of the first Brillouin zone including normal and Umklapp processes. The mean free paths of the charge carriers have been estimated too, to test the consistency of the delocalized description. The mobility values obtained for 300°K lie between $\text{30–100\hspace{0.17em}}{\mathrm{cm}}^2\hspace{0.17em}{\mathrm{V}}^{\text{−1}}·{\sec }^{\text{−1}}$ for models with bandwidths of 0.1–0.3 eV and between $\text{4–20\hspace{0.17em}}{\mathrm{cm}}^2\hspace{0.17em}{\mathrm{V}}^{\text{−1}}·{\sec }^{\text{−1}}$ for those with bandwidths of 0.02–0.1 eV, respectively. The temperature dependence follows the T⁻ⁿ law with n = 1.5–2 for the former and with n=2–2.5 for the latter group. The calculated mean free paths show real delocalization for the relatively broader bands, but the application of the band model seems to be questionable for the extremely narrow band cases.