Translational diffusion coefficients of macromolecules

The calculation of the translational diffusion coefficient of a single flexible polymer chain in dilute solution can be basically addressed either a) within the Einstein theory (calculating the time auto-correlation function of the macromolecule center of mass), or b) within the Kirkwood and Riseman theory for irreversible processes of macromolecules in solution. The equations of the latter theory can be solved employing different approximations that give rise to different values of the diffusion coefficient. In general, the value of the diffusion coefficient obtained through the different theories and approaches varies slightly depending on polymer features like flexibility. In this paper, we evaluate the most common procedures to compute the diffusion coefficient of flexible macromolecules via computer simulation and the difference between the values obtained.