Abstract
The quantum mechanical description of the chemical bond is generally given in terms of delocalized bonding orbitals, or, alternatively, in terms of correlations of occupations of localised orbitals. However, in the latter case, multiorbital correlations were treated only in terms of two-orbital correlations, although the structure of multiorbital correlations is far richer; and, in the case of bonds established by more than two electrons, multiorbital correlations represent a more natural point of view. Here, for the first time, we introduce the true multiorbital correlation theory, consisting of a framework for handling the structure of multiorbital correlations, a toolbox of true multiorbital correlation measures, and the formulation of the multiorbital correlation clustering, together with an algorithm for obtaining that. These make it possible to characterise quantitatively, how well a bonding picture describes the chemical system. As proof of concept, we apply the theory for the investigation of the bond structures of several molecules. We show that the non-existence of well-defined multiorbital correlation clustering provides a reason for debated bonding picture.
Highlights
The quantum mechanical description of the chemical bond is generally given in terms of delocalized bonding orbitals, or, alternatively, in terms of correlations of occupations of localised orbitals
Studying the two-orbital correlation pattern in molecular systems in equilibrium gives us the hint that the correlations must be related to the chemical bonds: strong two-orbital correlations can be observed between the orbitals which are involved in the given bond[8, 10, 12,13,14,15,16,17,18,19,20, 26]
We have presented a novel theory of the chemical bond which is inspired by quantum information theory and based on multiorbital correlations
Summary
The quantum mechanical description of the chemical bond is generally given in terms of delocalized bonding orbitals, or, alternatively, in terms of correlations of occupations of localised orbitals. We illustrate that in the debated case of the dicarbon molecule, there is no well-defined multiorbital correlation clustering, which provides a reason for the ambiguous bonding picture[29,30,31,32,33]. This is the first true multiorbital correlation based study of the chemical bond, and the first application of true multipartite correlation based techniques in physics. We note that our work is not connected to previous works of de Giambiagi, Giambiagi and Jorge[35] regarding generalised bond indices based on density-density correlation functions
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