Electron density,exchange-correlation density,and bond characterization from the perspective of the valence-bond theory.I.Two simple analytical cases

摘要

In this work,using a valence-bond wave function we obtain analytical expressions for the first- and second-order reduced density matrices of two simple,but quite representative,cases of diatomic molecular systems,namely,H_2 and LiH.A detailed study of their exchange-correlation density is performed for both equilibrium and nonequilibrium internuclear distances,discriminating the parallel- and antiparallel-spin contributions.The results show that the behavior of the exchange-correlation density clearly changes with the character of the bond,making it possible to obtain a good deal of information regarding the type of the bond interaction.