The inflection-point "gap" is determined as the distance between the average position of the C atoms and the inflection point of the Cu density profile (see Figure , 3 and S7). In order to determine the inflection point, we fit an error function to the electron density of Cu of which the inflection point and the half maximum coincide (see Figure ). This procedure is robust in comparison to numerically computing the second derivatives, which is prone to noise. We emphasize, that the σ for both the Gaussians and the error function only affects the electron density profile shape but not the determined Gr-Cu(l) gap if chosen reasonably large (see Figures and). Furthermore, the averaged Gr-Cu "gap" is computed over MD trajectory segments of 0.1 ns over the last 0.9 ns and the uncertainties are derived from the standard deviation between these segments.