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

The effect of molecular dissociation on the exchange-correlation Kohn-Sham potential vxc has been studied by the construction of vxc from the ab initio correlated density r for the monohydrides XH ~X5Li, B! at several bond distances R~X—H!. The molecular dissociation manifests itself in the formation of a characteristic peak of vxc in the bonding region. The partially integrated conditional probability amplitude F(s1 ,xW2 ,. . . ,xWNurW1) has been used to analyze the behavior of vxc by means of a partitioning into various components: the potential of the exchange-correlation hole vxc hole , the kinetic component vc ,kin, and the ‘‘response’’ component v resp . These components have been constructed from ab initio correlated firstand secondorder density matrices. The peak of vxc in the bonding region has been represented as a combination of the corresponding peak of vc ,kin and the positive buildup of v resp around the more electronegative atom H. Using the conditional amplitude analysis, the asymptotical expressions have been obtained for v 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 Ts , the kinetic part of the exchangecorrelation energy Tc , and the energy of the highest occupied molecular orbital eN on the bond distance has been studied. The results obtained have been compared with those for the homoatomic two-electron H2 molecule. @S1050-2947~96!03109-5#