On the Interpretation of the Source Function

摘要

The chemical information present in the source function (SF) is analyzed in several case studies bydecomposition into the relative contributions from the core and valence densities. Both experimental andquantum derived densities are examined, and for the latter case, the decomposition of the SF into contributionsfrom the individual Kohn—Sham molecular orbitals is also investigated. For pairs of atoms A and B, theorbital decomposition of the SF at the A—B bond critical point SF(A—B)_(bcp)is compared with that for thedelocalization index δ(Ω_A,Ω_B). For second and third period atoms, the valence density generally providesthe determining contribution to the total SF, but for heavier elements such as transition metals, the coredensity plays an increasingly important role. Moreover, when the reference point is close to the nodal planeof an orbital, this orbital makes a low to negligible contribution to the SF, which has clear implications forthe interpretation of π-interactions. This leads us to recommend caution in associating some chemical conceptswith features of the SF, especially for heavier elements.