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Insight into spin–orbital interaction using MCSCF method: A special analysis of the 1 Σ g + electronic state in C 2 and the linear polyacetylenic C 4 and C 6
Author(s) -
Zhu Changyan,
Zhang Xingxing,
Zhang Min,
Geng Yun,
Liu Xingman,
Su Zhongmin
Publication year - 2019
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.25814
Subject(s) - diradical , chemistry , singlet state , ionic bonding , state (computer science) , wave function , electron , atomic physics , triplet state , spin (aerodynamics) , molecular orbital , crystallography , computational chemistry , physics , quantum mechanics , molecule , excited state , ion , thermodynamics , organic chemistry , algorithm , computer science
The symmetry‐broken wave function can transform the 1 Σ g + state of C 2 from the classic double bonding to the quadruple bonding, where the transformed wave functions of ϕ L and ϕ R are singly occupied by two opposite‐spinning electrons. In this article, the effective bond order (EBO) contribution of the fourth bond in C 2 is assessed through the overlap integral between ϕ L and ϕ R , namely the value (0.60) is the EBO contribution of the fourth bond in the transformed scheme. Hence, the new EBO is 3.36, which is more equitable than the original EBO (2.15) in the traditional scheme. In addition, the singlet diradical character of the linear polyacetylenic C 4 and C 6 in the 1 Σ g + state is addressed for the first time. No spin‐polarized bonding exists in other linear C 2n clusters, because the ionic interaction in the polyacetylenic 1 Σ g + state of C 4 is negligible. Moreover, the coupling energy between α and β single electrons in C 4 is only 4.0 kcal mol −1 based on the electron spin‐flip energy. © 2019 Wiley Periodicals, Inc.