The effect of molecular dissociation on the exchange-correlation Kohn-Sham potential ${\mathit{v}}_{\mathrm{xc}}$ has been studied by the construction of ${\mathit{v}}_{\mathrm{xc}}$ from the ab initio correlated density ρ 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 ${\mathit{v}}_{\mathrm{xc}}$ in the bonding region. The partially integrated conditional probability amplitude Φ(${\mathit{s}}_1$, ${\mathit{x}\to }_2$,..., ${\mathit{x}\to }_{\mathit{N}}$|${\mathit{r}\to }_1$) has been used to analyze the behavior of ${\mathit{v}}_{\mathrm{xc}}$ by means of a partitioning into various components: the potential of the exchange-correlation hole ${\mathit{v}}_{\mathrm{xc}}^{\mathrm{hole}}$, the kinetic component ${\mathit{v}}_{\mathit{c},\mathrm{kin}}$, and the ‘‘response’’ component ${\mathit{v}}_{\mathrm{resp}}$. These components have been constructed from ab initio correlated first- and second-order density matrices. The peak of ${\mathit{v}}_{\mathrm{xc}}$ in the bonding region has been represented as a combination of the corresponding peak of ${\mathit{v}}_{\mathit{c},\mathrm{kin}}$ and the positive buildup of ${\mathit{v}}_{\mathrm{resp}}$ around the more electronegative atom H. Using the conditional amplitude analysis, the asymptotical expressions have been obtained for ${\mathit{v}}_{\mathrm{resp}}$ 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 ${\mathit{T}}_{\mathit{s}}$, the kinetic part of the exchange-correlation energy ${\mathit{T}}_{\mathit{c}}$, and the energy of the highest occupied molecular orbital ${\mathrm{\epsilon }}_{\mathit{N}}$ on the bond distance has been studied. The results obtained have been compared with those for the homoatomic two-electron ${\mathrm{H}}_2$ molecule. © 1996 The American Physical Society.

• Received 2 May 1996

DOI:https://doi.org/10.1103/PhysRevA.54.1957