The potential energy surface of the ground state of the water anion H2O− is carefully mapped

using multireference CI calculations for a large range of molecular geometries. Particular attention is paid

to a consistent description of both the O

−

+H2 and OH

−

+H asymptotes and to a relative position of

the anion energy to the ground state energy of the neutral molecule. The autodetachment region, where

the anion state crosses to the electronic continuum is identified. The local minimum in the direction of

the O− + H2 channel previously reported by Werner et al. [J. Chem. Phys. 87, 2913 (1987)] is found

to be slighly off the linear geometry and is separated by a saddle from the autodetachment region. The

autodetachment region is directly accessible from the OH

−

+H asymptote. For the molecular geometries in

the autodetachment region and in its vicinity we also performed fixed-nuclei electron-molecule scattering

calculations using the R-matrix method. Tuning of consistency of a description of the correlation energy in

both the multireference CI and R-matrix calculations is discussed. Two models of the correlation energy

within the R-matrix method that are consistent with the quantum chemistry calculations are found. Both

models yield scattering quantities in a close agreement. The results of this work will allow a consistent

formulation of the nonlocal resonance model of the water anion in a future publication.

using multireference CI calculations for a large range of molecular geometries. Particular attention is paid

to a consistent description of both the O

−

+H2 and OH

−

+H asymptotes and to a relative position of

the anion energy to the ground state energy of the neutral molecule. The autodetachment region, where

the anion state crosses to the electronic continuum is identified. The local minimum in the direction of

the O− + H2 channel previously reported by Werner et al. [J. Chem. Phys. 87, 2913 (1987)] is found

to be slighly off the linear geometry and is separated by a saddle from the autodetachment region. The

autodetachment region is directly accessible from the OH

−

+H asymptote. For the molecular geometries in

the autodetachment region and in its vicinity we also performed fixed-nuclei electron-molecule scattering

calculations using the R-matrix method. Tuning of consistency of a description of the correlation energy in

both the multireference CI and R-matrix calculations is discussed. Two models of the correlation energy

within the R-matrix method that are consistent with the quantum chemistry calculations are found. Both

models yield scattering quantities in a close agreement. The results of this work will allow a consistent

formulation of the nonlocal resonance model of the water anion in a future publication.

typ: | article |
---|---|

journal: | European Physical Journal D |

volume: | 70 |

pages: | 107 |

year: | 2016 |

grant: | GACR 0503 |

files: |
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eur.phys.j. d70 (2016) 107 (houfek, cizek).pdf (1727.1 kB) |