Effect of Pauli repulsion on the molecular exchange-correlation Kohn-Sham potential: A comparative calculation ofNe2andN2

The Pauli repulsion between closed shells of two interacting systems induces structure in the exchange-correlation Kohn-Sham potential ${\nu }_{\mathrm{xc}}.$ This effect has been studied by the construction of ${\nu }_{\mathrm{xc}}$ from the ab initio correlated density ρ for the ${\mathrm{Ne}}_2$ dimer. Pauli repulsion manifests itself in the formation of a characteristic bond midpoint peak of ${\nu }_{\mathrm{xc}}.$ The behavior of ${\nu }_{\mathrm{xc}}$ has been analyzed by means of a partitioning into various components: the potential of the exchange-correlation hole ${\nu }_{\mathrm{xc}}^{\mathrm{hole}},$ the kinetic component ${\nu }_{c,\mathrm{kin}},$ and the “response” component ${\nu }_{\mathrm{resp}}.$ These components have been constructed from ab initio first- and second-order density matrices. All the components display bond midpoint peaks that contribute to the corresponding peak of ${\nu }_{\mathrm{xc}}.$ The peaks of ${\nu }_{\mathrm{xc}}^{\mathrm{hole}}$ and ${\nu }_{c,\mathrm{kin}}$ have been interpreted in terms of localization and mobility of the exchange-correlation hole, while the peak of ${\nu }_{\mathrm{resp}}$ is related to the Pauli repulsion with the help of the approximation of Krieger-Li-Iafrate for this potential. The results obtained have been compared with those for the ${\mathrm{N}}_2$ molecule.