exp(-ar)/r * (1 + r/2)
the first part (the "1"-part) stems from the proton and the other part is
due to the electrondistribution.
the potential has the following shape:
accordingly to the laplacian-equation we get the charge ditribution by :
laplacian (phi) = 4 pi rho
we also can plot this function, what gives us the following plot:
or if we only make a plot of the elecrondistribution alone, we get the
following diagram: