The Electronic Structure and Bonding in Some Small Molecules

The electronic structures of the first- and second-row homonuclear diatomics, XeF<sub>2</sub>, and the weakly bound dimers of nitric oxide and nitrogen dioxide molecules in their ground states are discussed in terms of molecular orbital (MO) theory and, where possible, valence bond theor...

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Main Author: George B. Bacskay
Format: Article
Language:English
Published: MDPI AG 2025-03-01
Series:Molecules
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Online Access:https://www.mdpi.com/1420-3049/30/5/1154
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author George B. Bacskay
author_facet George B. Bacskay
author_sort George B. Bacskay
collection DOAJ
description The electronic structures of the first- and second-row homonuclear diatomics, XeF<sub>2</sub>, and the weakly bound dimers of nitric oxide and nitrogen dioxide molecules in their ground states are discussed in terms of molecular orbital (MO) theory and, where possible, valence bond theories. The current work is extended and supported by restricted and unrestricted Hartree–Fock (RHF and UHF) self-consistent field (SCF), complete active space SCF (CASSCF), multi-reference configuration interaction (MRCI), coupled cluster CCSD(T), and unrestricted Kohn–Sham (UKS) density functional calculations using a polarized triple-zeta basis. The dicarbon (C<sub>2</sub>) molecule is especially poorly described by RHF theory, and it is argued that the current MO theories taught in most undergraduate courses should be extended in recognition of the fact that the molecule requires at least a two-configuration treatment.
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spelling doaj-art-7dd02bdbd6f94a6bba3b3234ccb757432025-08-20T02:06:12ZengMDPI AGMolecules1420-30492025-03-01305115410.3390/molecules30051154The Electronic Structure and Bonding in Some Small MoleculesGeorge B. Bacskay0School of Chemistry, The University of Sydney, Sydney, NSW 2006, AustraliaThe electronic structures of the first- and second-row homonuclear diatomics, XeF<sub>2</sub>, and the weakly bound dimers of nitric oxide and nitrogen dioxide molecules in their ground states are discussed in terms of molecular orbital (MO) theory and, where possible, valence bond theories. The current work is extended and supported by restricted and unrestricted Hartree–Fock (RHF and UHF) self-consistent field (SCF), complete active space SCF (CASSCF), multi-reference configuration interaction (MRCI), coupled cluster CCSD(T), and unrestricted Kohn–Sham (UKS) density functional calculations using a polarized triple-zeta basis. The dicarbon (C<sub>2</sub>) molecule is especially poorly described by RHF theory, and it is argued that the current MO theories taught in most undergraduate courses should be extended in recognition of the fact that the molecule requires at least a two-configuration treatment.https://www.mdpi.com/1420-3049/30/5/1154covalent bondingquantum chemistryelectronic structuremolecular orbital theoryvalence bond theorydensity functional theory
spellingShingle George B. Bacskay
The Electronic Structure and Bonding in Some Small Molecules
Molecules
covalent bonding
quantum chemistry
electronic structure
molecular orbital theory
valence bond theory
density functional theory
title The Electronic Structure and Bonding in Some Small Molecules
title_full The Electronic Structure and Bonding in Some Small Molecules
title_fullStr The Electronic Structure and Bonding in Some Small Molecules
title_full_unstemmed The Electronic Structure and Bonding in Some Small Molecules
title_short The Electronic Structure and Bonding in Some Small Molecules
title_sort electronic structure and bonding in some small molecules
topic covalent bonding
quantum chemistry
electronic structure
molecular orbital theory
valence bond theory
density functional theory
url https://www.mdpi.com/1420-3049/30/5/1154
work_keys_str_mv AT georgebbacskay theelectronicstructureandbondinginsomesmallmolecules
AT georgebbacskay electronicstructureandbondinginsomesmallmolecules