Extraction of local spin-coupled states by second quantized operators

We present a methodology for analyzing chemical bonds embedded in the electronic wave function of molecules, especially in terms of spin correlations or so-called local spin. In this paper, based on biorthogonal second quantization, the spin correlation functions of molecules are naturally introduced, which enables us to extract local singlet and local triplet elements from the wave function. We also clarify the relationship between these spin correlations and traditional chemical concepts, i.e., resonance structures. Several chemical reactions, including the intramolecular radical cyclization and the formation of preoxetane, are demonstrated to verify the analysis method numerically.

Automated summary

This paper presents a methodology for analyzing chemical bonds in molecules using spin correlations in the electronic wave function. By introducing spin correlation functions using biorthogonal second quantization, the method can extract local singlet and local triplet elements. The relationship between these spin correlations and traditional chemical concepts is clarified, and the analysis method is numerically verified through chemical reactions.