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

Abstract

The Pauli repulsion between closed shells of two interacting systems induces structure in the exchange-correlation Kohn-Sham potential ${\ensuremath{\nu}}_{\mathrm{xc}}.$ This effect has been studied by the construction of ${\ensuremath{\nu}}_{\mathrm{xc}}$ from the ab initio correlated density \ensuremath{\rho} for the ${\mathrm{Ne}}_{2}$ dimer. Pauli repulsion manifests itself in the formation of a characteristic bond midpoint peak of ${\ensuremath{\nu}}_{\mathrm{xc}}.$ The behavior of ${\ensuremath{\nu}}_{\mathrm{xc}}$ has been analyzed by means of a partitioning into various components: the potential of the exchange-correlation hole ${\ensuremath{\nu}}_{\mathrm{xc}}^{\mathrm{hole}},$ the kinetic component ${\ensuremath{\nu}}_{c,\mathrm{kin}},$ and the ``response'' component ${\ensuremath{\nu}}_{\mathrm{resp}}.$ 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 ${\ensuremath{\nu}}_{\mathrm{xc}}.$ The peaks of ${\ensuremath{\nu}}_{\mathrm{xc}}^{\mathrm{hole}}$ and ${\ensuremath{\nu}}_{c,\mathrm{kin}}$ have been interpreted in terms of localization and mobility of the exchange-correlation hole, while the peak of ${\ensuremath{\nu}}_{\mathrm{resp}}$ 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.