Structures and thermochemistry of the alkali metal monoxide anions, monoxide radicals, and hydroxides

Benjamin Mintz, Bun Chan, Michael B. Sullivan, Thomas Buesgen, Anthony P. Scott, Steven R. Kass, Leo Radom*, Angela K. Wilson

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    15 Citations (Scopus)

    Abstract

    The geometries, enthalpies of formation (ΔH° f), separations of electronic states, electron affinities, gas-phase acidities, and bond dissociation energies associated with the alkali metal monoxide anions (MO -), monoxide radicals (MO .), and hydroxides (MOH) (M = Li, Na, and K) have been investigated using single-reference and multireference variants of the WnC procedures. Our best estimates of the ΔH° f values for the ground states at 298 K are as follows: 8.5 ( 3π LiO -), 48.5 ( 2π LiO), -243.4 ( 1σ + LiOH), 34.2 ( 3π NaO -), 86.4 ( 2π NaO .), -190.8 ( 1σ + NaOH), 15.1 ( 1σ + KO -), 55.9 ( 2σ + KO .), and -227.0 ( 1σ+ KOH) kJ mol -1. While the LiO . and NaO . radicals have 2π ground states, for KO ., the 2π+ and 2π electronic states lie very close in energy, with our best estimate being a preference for the 2σ + state by 1.1 kJ mol -1 at 0 K. In a similar manner, the ground state for MO - changes from 3π for LiO - and NaO - to 1π + for KO -. The 1σ + state of KO - is indicated by the calculated 1 diagnostic and the SCF contribution to the total atomization energy to have a significant degree of multireference character. This leads to a difference of more than 100 kJ mol -1 between the single-reference W2C and multireference W2C-CAS-ACPF and W2C-CAS-AQCC estimates for the 1σ + δH° f for KO -.

    Original languageEnglish
    Pages (from-to)9501-9510
    Number of pages10
    JournalJournal of Physical Chemistry A
    Volume113
    Issue number34
    DOIs
    Publication statusPublished - 27 Aug 2009

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