The biased two-electrode configurations consist of two gold slabs separated by vacuum (Figure ) or by a 1,4-dithiol-phenylene molecular junction (Figure ). The configuration in Figure The FD Poisson solver is known to be unstable for highly elongated cells and it could reach convergence for the two-electrode setup with a long and narrow cell. Hence, the two-electrode cell calculations could not be performed in the presence of the dielectric solvent. We therefore simulated the system in vacuum using the newly implemented FastPoissonSolver, which is the now the default Poisson solver in GPAW and which was observed to be stable and to provide converged results. However, FastPoissonSolver is not yet compatible with GPAW's dielectric solvent model or the counter charges used in SJM. For these reasons, we omitted the dielectric solvent from these two-electrode simulations and kept the simulation cell charge neutral. These omissions do not, however, the conclusion that bias across a two-electrode simulation cell can be simulated with CIP-cDFT.