✍ Scribed by Renzo Cimiraglia; Raffaele Resta
No coin nor oath required. For personal study only.
The shape of correlation holes in many‐electron systems is at present scarcely known, even where correlated wave functions are available. We investigate here the kind of electron correlation brought about by configuration interaction (CI), within a given basis set, in the wavefunction of a polyatomic system. The model ring system H~6~ (in two different bonding circumstances) and H~14~ have been chosen for a detailed study, because of their paradigmatic importance. We set out the equal‐spin and different‐spin correlation holes as obtained from complete CI calculations in H6 and partial ct in H~14~, both within a minimal basis set. We basically find the spinless correlation as being short range, while the spin‐dependent correlation holes show long‐range oscillations of antiferromagnetic character. We also present a natural spin‐geminal analysis of the two‐body reduced density matrices in these systems; we find a peculiarity possibly related to the long‐range correlation discussed above. Finally, we compare the electron correlation as given from our CI wavefunction to other pictures of electron correlation, as obtained essentially from alternant molecular orbital wave functions and from the electron–gas literature.
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