Coupled-cluster and explicitly correlated perturbation-theory calculations of the uracil anion.
A valence-type anion of the canonical tautomer of uracil has been characterized using explicitly correlated second-order Moller-Plesset perturbation theory (RI-MP2-R12) in conjunction with conventional coupled-cluster theory with single, double, and perturbative triple excitations. At this level of electron-correlation treatment and after inclusion of a zero-point vibrational energy correction, determined in the harmonic approximation at the RI-MP2 level of theory, the valence anion is adiabatically stable with respect to the neutral molecule by 40 meV. The anion is characterized by a vertical detachment energy of 0.60 eV. To obtain accurate estimates of the vertical and adiabatic electron binding energies, a scheme was applied in which electronic energy contributions from various levels of theory were added, each of them extrapolated to the corresponding basis-set limit. The MP2 basis-set limits were also evaluated using an explicitly correlated approach, and the results of these calculations are in agreement with the extrapolated values. A remarkable feature of the valence anionic state is that the adiabatic electron binding energy is positive but smaller than the adiabatic electron binding energy of the dipole-bound state.
Bachorz
Rafał A
RA
Center for Functional Nanostructures (CFN), Universität Karlsruhe (TH), D-76128 Karlsruhe, Germany.
Klopper
Wim
W
Gutowski
Maciej
M
D000838:Anions; D008956:Models, Chemical; D011789:Quantum Theory; D013816:Thermodynamics; D014498:Uracil / Q000737:chemistry*
D000838:Anions; D014498:Uracil