Ab initio study on the spectroscopy of CuCl2. II. Benchmark calculations on the $X^{2}\Pi_{g} - C^{2}\Delta_{g}$ and $X^{2}\Pi_{g} - D^{2}\Delta_{g}$ transitions. - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Journal of Chemical Physics Année : 2004

Ab initio study on the spectroscopy of CuCl2. II. Benchmark calculations on the $X^{2}\Pi_{g} - C^{2}\Delta_{g}$ and $X^{2}\Pi_{g} - D^{2}\Delta_{g}$ transitions.

Résumé

The $X^{2}\Pi_{g} - C^{2}\Delta_{g}$ and $X^{2}\Pi_{g} - D^{2}\Delta_{g}$ transitions on CuCl2 have been studied using the most sophisticated non-dynamic and dynamic electronic correlation treatments. We report here ab initio benchmark calculations using especially developed basis sets to study, at the CASSCF+CASPT2 and CASSCF+ACPF levels, the transition energies as well as the corresponding equilibrium geometries. The spin-orbit (SO) effects of both atoms were included in a second step through the effective hamiltonian formalism, using the calibrated SO effective potentials developed by the Stuttgart group. Without SO at the CASSCF+ACPF level, the vertical excitation energy for the $^{2}\Delta_{g}$ state is 6711 cm-1 and the symmetric stretching equilibrium Cu-Cl distance is 4.04 a.u. The inclusion of the SO effects leads to a pure $^{2}\Delta_{g} \Omega$=5/2 C state and a $\Omega$=3/2 (0.7% $^{2}\Pi_{g}$, 99.3% $^{2}\Delta_{g}$) D state. The calculated transition energies for the C and D states are 6340 and 8020 cm-1, in good agreement with the spin-orbit splitting recent values from gas-phase and rare-gas matrix isolation laser induced fluorescence experiments. The present benchmark results show, as was recently done for the $X^{2}\Pi_{g}- ^{2}\Sigma_{g}$ transition, the rather poor performance of all the DFT-based descriptions for the $^{2}\Delta_{g}$ state, which largely overestimate its Te, systematically placing it around 19,000 cm-1. The CASSCF+CASPT2 method also overestimates, by around 50%, the $X^{2}\Pi_{g}- ^{2}\Delta_{g}$ transition energy, showing that only large variational calculations can produce reliable spectroscopic results for this kind of complex systems where delicate electronic correlation effects have to be carefully dealt with.
Fichier principal
Vignette du fichier
cucl2.pdf (157.88 Ko) Télécharger le fichier
Loading...

Dates et versions

hal-00003672 , version 1 (22-12-2004)

Identifiants

  • HAL Id : hal-00003672 , version 1

Citer

Alejandro Ramírez-Solís, Jean-Pierre Daudey. Ab initio study on the spectroscopy of CuCl2. II. Benchmark calculations on the $X^{2}\Pi_{g} - C^{2}\Delta_{g}$ and $X^{2}\Pi_{g} - D^{2}\Delta_{g}$ transitions.. Journal of Chemical Physics, 2004, 122, pp.014315. ⟨hal-00003672⟩
71 Consultations
252 Téléchargements

Partager

Gmail Facebook X LinkedIn More