This figure shows the smooth dielectric function used in this work for a single atom with σ = 0.95Å, εin = 12, εext = 1 and A = 10.0 (Cl of the G1-12 set). In a), starting from the center of the atom (r = 0), the dielectric stays constant until the ‘density’, expressed with a sum of Gaussian (pink curve), reaches a certain small value that cause the dielectric to smoothly reach the external dielectric value. The steepness and the position of the switching region depend on the value of the A parameter.