Per-Åke Malmqvist
Senior lecturer
A CASPT2 study of the valence and lowest Rydberg electronic states of benzene and phenol.
Author
Summary, in English
The valence excited states and the 3s, 3p, and 3d
(united atom) Rydberg states of benzene and phenol have been obtained by
the CASPT2 method, which computes a second-order perturbation
correction to complete active space self-consistent field (CASSCF)
energies. All non-zero dipole oscillator strengths are also computed, at
the CASSCF level. For benzene, 16 singlet and 16 triplet states with
excitation energies up to ca. 7.86 eV (63 400 cm–1) are
obtained. Of these, 12 singlet and three triplet energies are
experimentally known well enough to allow meaningful comparison. The
average error is around 0.1 eV. The highest of these singlet states (21 E2g)
is the highest valence ππ* state predicted by elementary π-electron
theory. Its energy is then considerably lower than has been suggested
from laser flash experiments, but in perfect agreement with a
reinterpretation of that experiment. For phenol, 27 singlet states are
obtained, in the range 4.53–7.84 eV (63 300 cm−1). Only the
lowest has a well-known experimental energy, which agrees with the
computed result within 0.03 eV. The ionization energy is in error by
0.05 eV.
(united atom) Rydberg states of benzene and phenol have been obtained by
the CASPT2 method, which computes a second-order perturbation
correction to complete active space self-consistent field (CASSCF)
energies. All non-zero dipole oscillator strengths are also computed, at
the CASSCF level. For benzene, 16 singlet and 16 triplet states with
excitation energies up to ca. 7.86 eV (63 400 cm–1) are
obtained. Of these, 12 singlet and three triplet energies are
experimentally known well enough to allow meaningful comparison. The
average error is around 0.1 eV. The highest of these singlet states (21 E2g)
is the highest valence ππ* state predicted by elementary π-electron
theory. Its energy is then considerably lower than has been suggested
from laser flash experiments, but in perfect agreement with a
reinterpretation of that experiment. For phenol, 27 singlet states are
obtained, in the range 4.53–7.84 eV (63 300 cm−1). Only the
lowest has a well-known experimental energy, which agrees with the
computed result within 0.03 eV. The ionization energy is in error by
0.05 eV.
Department/s
- Computational Chemistry
Publishing year
1995-04
Language
English
Pages
91-108
Publication/Series
Theoretica Chimica Acta
Volume
91
Document type
Journal article
Publisher
Springer
Topic
- Theoretical Chemistry (including Computational Chemistry)
Status
Published
ISBN/ISSN/Other
- ISSN: 0040-5744