Effect of molecular dissociation on the exchange-correlation Kohn-Sham potential

The effect of molecular dissociation on the exchange-correlation Kohn-Sham potential upsilon(xc) has been studied by the construction of upsilon(xc) from the ab initio correlated density rho for the monohydrides XH (X=Li, B) at several bond distances R(X-H), The molecular dissociation manifests itself in the formation of a characteristic peak of upsilon(xc) in the bonding region. The partially integrated conditional probability amplitude Phi(s(1),<(x)over right arrow (2)>,...,<(x)over right arrow (N)>\<(r)over right arrow (1)>) has been used to analyze the behavior of upsilon(xc) by means of a partitioning into various components: the potential of the exchange-correlation hole upsilon(xc)(hole), the kinetic component upsilon(c,kin), and the ''response'' component upsilon(resp). These components have been constructed from ab initio correlated first- and second-order density matrices. The peak of upsilon(xc) in the bonding region has been represented as a combination of the corresponding peak of upsilon(c,kin) and the positive buildup of upsilon(resp) around the more electronegative atom H. Using the conditional amplitude analysis, the asymptotical expressions have been obtained for upsilon(resp) and its positive buildup for the general case of a heteroatomic molecule AB. The dependence of the Kohn-Sham energy characteristics such as the kinetic energy of noninteracting particles T-s, the kinetic part of the exchange-correlation energy T-c, and the energy of the highest occupied molecular orbital epsilon(N) on the bond distance has been studied. The results obtained have been compared with those for the homoatomic two-electron H-2 molecule.