Comment on "Dynamical corrections to the DFT-LDA electron conductance in nanoscale systems"

In a recent paper Sai et al. [1] identified a correction R^{dyn}$ to the DC conductance of nanoscale junctions arising from dynamical exchange-correlation (XC) effects within time-dependent density functional theory. This quantity contributes to the total resistance through $R=R_{s}+R^{dyn}$ where $R_{s}$ is the resistance evaluated in the absence of dynamical $XC$ effects. In this Comment we show that the numerical estimation of $R^{dyn}$ in example systems of the type they considered should be considerably reduced, once a more appropriate form for the shear electron viscosity ¿ is used.