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

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14 Scopus citations

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 (US)
Pages (from-to)9501-9510
Number of pages10
JournalJournal of Physical Chemistry A
Volume113
Issue number34
DOIs
StatePublished - Aug 27 2009

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