  We describe an approach based on non-equilibrium molecular dynamics (NEMD)
simulations to calculate the ionic mobility of solid ion conductors such as
solid electrolytes from first-principles. The calculations are carried out in
finite slabs of the material, where an electric field is applied and the
dynamic response of the mobile ions is measured. We compare our results with
those obtained from diffusion calculations, under the non-interacting ion
approximation, and with experiment. This method is shown to provide good
quantitative estimates for the ionic mobilities of two silver conductors,
$\alpha$-AgI and $\alpha$-RbAg$_4$I$_5$. In addition to being convenient and
numerically robust, this method accounts for ion-ion correlations at a much
lower computational cost than exact approaches.
