10.1021/acs.jpca.7b07054.s001 Aaron C. West Aaron C. West Juan J. Duchimaza-Heredia Juan J. Duchimaza-Heredia Mark S. Gordon Mark S. Gordon Klaus Ruedenberg Klaus Ruedenberg Identification and Characterization of Molecular Bonding Structures by ab initio Quasi-Atomic Orbital Analyses American Chemical Society 2017 ab initio amplifications quasi-atomic orbitals quasi-atomic analysis ab initio counterparts Molecular Bonding Structures molecule ab initio wave functions ab initio ab initio Quasi-Atomic Orbital Analyses Lewis dot symbols bond orders 2017-11-14 18:51:17 Journal contribution https://acs.figshare.com/articles/journal_contribution/Identification_and_Characterization_of_Molecular_Bonding_Structures_by_ab_initio_Quasi-Atomic_Orbital_Analyses/5601361 The quasi-atomic analysis of <i>ab initio</i> electronic wave functions in full valence spaces, which was developed in preceding papers, yields oriented quasi-atomic orbitals in terms of which the <i>ab initio</i> molecular wave function and energy can be expressed. These oriented quasi-atomic orbitals are the rigorous <i>ab initio</i> counterparts to the conceptual bond forming atomic hybrid orbitals of qualitative chemical reasoning. In the present work, the quasi-atomic orbitals are identified as bonding orbitals, lone pair orbitals, radical orbitals, vacant orbitals and orbitals with intermediate character. A program determines the bonding characteristics of all quasi-atomic orbitals in a molecule on the basis of their occupations, bond orders, kinetic bond orders, hybridizations and local symmetries. These data are collected in a record and provide the information for a comprehensive understanding of the synergism that generates the bonding structure that holds the molecule together. Applications to a series of molecules exhibit the complete bonding structures that are embedded in their <i>ab initio</i> wave functions. For the strong bonds in a molecule, the quasi-atomic orbitals provide quantitative <i>ab initio</i> amplifications of the Lewis dot symbols. Beyond characterizing strong bonds, the quasi-atomic analysis also yields an understanding of the weak interactions, such as vicinal, hyperconjugative and radical stabilizations, which can make substantial contributions to the molecular bonding structure.