Nonadditivity of ab initio pair potentials for molecular dynamics of multivalent transition metal ions in water

Larry A. Curtiss, J. Woods Halley, Joseph Hautman, Aneesur Rahman

Research output: Contribution to journalArticlepeer-review

143 Scopus citations

Abstract

Ab initio molecular orbital pair potentials for the interaction of Fe 2+ and Fe3+ ions with H2O are reported. Molecular dynamics calculations of the static structure of the solvation shell of Fe2+ and Fe3+ in water using the ab initio pair potentials gives physically incorrect results, i.e., the coordination numbers are eight instead of six as observed experimentally. This problem has also been encountered by other workers for divalent transition metal ions in water. By computing three-body energies from the interaction of two water molecules with the cations, we show that the origin of the problem is most likely in the assumption of the additivity of the pair potentials, i.e., neglect of many-body forces. Empirical potentials are reported which take approximate account of the three-body forces and give coordination numbers of six for both Fe2+ and Fe3+ in water.

Original languageEnglish (US)
Pages (from-to)2319-2327
Number of pages9
JournalThe Journal of chemical physics
Volume86
Issue number4
DOIs
StatePublished - Jan 1 1986

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