Comparison of Charge Densities and Pseudo Charge Densities forSi2

We compare the charge densities of the orbitals of ${\mathrm{Si}}_2$ calculated from Hartree-Fock-Slater self-consistent-field wave functions and pseudo charge densities from a local pseudopotential and found considerable differences. Given that the former are correct, this means that physically misleading conclusions could be drawn from the pseudo charge density. While pseudopotential methods have added much insight, current pseudocharge calculations for molecules and surfaces could be unreliable indicators of the true charge density.