Effect of Pauli repulsion on the molecular exchange-correlation Kohn-Sham potential:: A comparative calculation of Ne2 and N2

The Pauli repulsion between closed shells of two interacting systems induces structure in the exchange-correlation Kohn-Sham potential nu(xc). This effect has been studied by the construction of nu(xc) from the nb initio correlated density rho for the Ne-2 dimer. Pauli repulsion manifests itself in the formation of a characteristic bond midpoint peak of nu(xc). The behavior of nu(xc) has been analyzed by means of a partitioning into various components: the potential of the exchange-correlation hole nu(xc)(hole), the kinetic component nu(c,kin), and the "response" component nu(resp) These components have been constructed from nb initio first-and second-order density matrices. All the components display bond midpoint peaks that contribute to the corresponding peak of nu(xc). The peaks of nu(xc)(hole) and nu(c,kin) have been interpreted in terms of localization and mobility of the exchange correlation hole, while the peak of nu(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 N-2 molecule.