Open AccessInsights into the Perplexing Nature of the Bonding in C2 from Generalized Valence Bond Calculations
Author(s) -
Lü Xu,
Thom H. Dunning
Publication year - 2013
Publication title -
journal of chemical theory and computation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.001
H-Index - 185
eISSN - 1549-9626
pISSN - 1549-9618
DOI - 10.1021/ct400867h
Subject(s) - generalized valence bond , wave function , valence bond theory , quadruple bond , covalent bond , pairing , chemical bond , chemistry , diatomic molecule , atomic orbital , triple bond , singlet state , valence (chemistry) , electronic structure , modern valence bond theory , bond order , valence electron , electron pair , atomic physics , single bond , computational chemistry , electron , quantum mechanics , molecule , bond length , physics , excited state , group (periodic table) , double bond , superconductivity , polymer chemistry
Diatomic carbon, C2, has been variously described as having a double, triple, or quadruple bond. In this article, we report full generalized valence bond (GVB) calculations on C2. The GVB wave function-more accurate than the Hartree-Fock wave function and easier to interpret than traditional multiconfiguration wave functions-is well-suited for characterizing the bonding in C2. The GVB calculations show that the electronic wave function of C2 is not well described by a product of singlet-coupled, shared electron pairs (perfect pairing), which is the theoretical basis for covalent chemical bonds. Rather, C2 is best described as having a traditional covalent σ bond with the electrons in the remaining orbitals of the two carbon atoms antiferromagnetically coupled. However, even this description is incomplete as the perfect pairing spin function also makes a significant contribution to the full GVB wave function. The complicated structure of the wave function of C2 is the source of the uncertainty about the nature of the bonding in this molecule.