I recently computed contour plots of both graphene and hexagonal boron nitride monolayer in intralayer planes and planes perpendicular to the layers that bisect the bonds in these layers. There are three of these plots for each plane type, and I am already able to understand the contour plots generated by 'CalculateElectrostaticDifference', which provides a plot similar to the molecular electrostatic potential (MEP) surface. I also am able to interpret the plots produced by 'CalculateElectronDensity', which shows the electron density independent of orbitals in the substances. However, I am not able to get adequate understanding of 'CalculateEffectivePotential', which gives the Kohn-Sham effective potential, V(eff), of the system.
What kind of utility is obtained by calculating contours of the Kohn-Sham effective potential? I notice that the contour plots of 'effective potential' have values that never become positive, unlike the electron density plots (which have positive values). How does one interpret the Kohn-Sham effective potential in terms of the atoms of a system?