Small-polaron resistivity of the narrow band molecular chain: The influence of phonon hardening

We study the effect of the small-polaron induced changes of phonon spectra on charge transfer in molecular solids. Noticeable discrepancy with the predictions of the traditional small-polaron theories is observed: accounting of phonon hardening yields significantly lower estimates for small-polaron resistivity than that obtained on the basis of conventional approaches. This especially concerns the low temperature limit in which transport processes are dominated by the band like motion of charge carriers. This difference gradually disappears with the increasing of coupling constant and temperature