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On the Ordering of Orbital Energies in High-Spin ROHF

TitleOn the Ordering of Orbital Energies in High-Spin ROHF
Publication TypeJournal Article
Year of Publication2010
AuthorsGlaesemann KR, Schmidt MW
Journal TitleJournal of Physical Chemistry A
Volume114
Pages8772-8777
Date Published08/26
ISBN Number1089-5639
Accession NumberISI:000280962400029
Keywordsab-initio, consistent-field theory, correlated wave-functions, degenerate perturbation-theory, excited-states, hartree-fock theory, hole states, minimal basis-sets, molecular-orbitals, open-shell systems
Abstract

The restricted open-shell Hartree-Fock (ROHF) method is a standard tool used by quantum chemists for studying molecules with unpaired electrons In this work a problem with some implementations of the ROHF. method is presented along with an elegant solution. The ground state (2)A(2) potential energy surface of the 5,5'-(4H, 4H')-spirobi[cyclopenta[c]pyrrole]-2,2'6,6'-tetrahydro cation is the molecular test case, which elucidates the underlying problem For this molecule, four distinct ROHF perturbation theories yield smooth (and parallel) potential energy curves The arbitrariness of the ROHF orbital energies is illustrated with diatomic CN. The method proposed will also fix Aufbau principle violations reported by Plakhutin and Davidson [Plakhutin, B N, Davidson, E R J. Phys. Chem. A 2009, 113, 12386-12395]
URL<Go to ISI>://000280962400029
DOI10.1021/Jp101758y