Ground state of the (H<inf>2</inf>O)<inf>2</inf><sup>+</sup> radical cation: DFT versus post-Hartree - Fock methods

Mariona Sodupe, Juan Bertran, Luis Rodríguez-Santiago, E. J. Baerends

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217 Citations (Scopus)

Abstract

Correlated calculations show the proton-transferred OH-H3O+ isomer to be the ground-state structure of the (H2O)2+ dimer ion, with the C2h hemibond structure being ca. 8 kcal/mol less stable. Modern density functionals however favor the hemibond structure, overestimating the strength of the three-electron bond by ca. 17 kcal/ mol. The wrong prediction of the relative stability of the two isomers is attributed to overestimation by the exchange functionals of the self-interaction part of the exchange energy in the hemibond ion due to its delocalized electron hole. It is cautioned that this erroneous behavior of the density functionals for exchange, if unrecognized, may lead to wrong predictions for ground-state structures of systems with a three-electron bond. © 1999 American Chemical Society.
Original languageEnglish
Pages (from-to)166-170
JournalJournal of Physical Chemistry A
Volume103
Issue number1
Publication statusPublished - 7 Jan 1999

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