π-electron charge densities have been generated with Multiwfn 167 software. To see the effect of the perturbation (external point charge) on the electronic structure of the carbon chains, the volumetric charge densities obtained for the unperturbed structure of cumulene and polyyne have been subtracted from the perturbed structures. To analyze the data, the volumetric charge density difference ∆ϱ(x, y, z) along the carbon chain has been summed over the axis perpendicular to the carbon chain, obtaining the surface charge density difference ∆σ(x, y) depicted for both cumulene and polyyne in Fig. . This figure shows a clear Friedel oscillations pattern, with electron density decaying along the carbon chain.