کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5429328 | 1397346 | 2011 | 12 صفحه PDF | دانلود رایگان |
The potential energy curves (PECs) of eight low-lying electronic states (X2Σ+, A2Î , B2Σ+, a4Σ+, D2Î , E2Σ+, 12Σâ and F2Î) of the CN radical have been studied using the ab initio quantum chemical method. The calculations have been performed using the complete active space self-consistent field (CASSCF) method followed by the valence internally contracted multireference configuration interaction (MRCI) approach in combination with the correlation-consistent basis sets of Dunning and co-workers. The effects on the PECs by the core-valence correlation and relativistic corrections are taken into account. The way to consider the relativistic correction is to use the second-order Douglas-Kroll Hamiltonian approximation. The core-valence correlation correction calculations are performed with the cc-pCVQZ basis set. The relativistic correction is carried out at the level of cc-pV5Z basis set. In order to obtain more reliable results, the PECs determined by the MRCI calculations are also corrected for size-extensivity errors by means of the Davidson modification (MRCI+Q). The PECs are extrapolated to the complete basis set (CBS) limit by the total-energy extrapolation scheme. With these PECs, the spectroscopic parameters (Te, Re, Ïe, Ïexe, ÏeÑe, Be, αe and γe) are determined and compared with those reported in the literature. Finally, with the PECs obtained by the MRCI+Q/CV+DK+Q5 calculations, the complete vibrational states are computed for the eight electronic states by solving the ro-vibrational Schrödinger equation for the non-rotating radical, and the vibrational levels and inertial rotation and centrifugal distortion constants of the first 11 vibrational states are reported, which agree favorably with the available experimental data. The spectroscopic parameters of 12Σâ and F2Î electronic states obtained by the MRCI+Q/CV+DK+Q5 calculations should be good predictions for future laboratory experiments.
⺠Effect on the PECs by the core-valence correlation and relativistic corrections is included. ⺠PECs obtained by the MRCI and MRCI+Q are extrapolated to the CBS limit. ⺠Extrapolation obviously improves the quality of spectroscopic parameters. ⺠Spectroscopic parameters extrapolated to the CBS limit achieve much high accuracy. ⺠Molecular constants are calculated by the PECs extrapolated.
Journal: Journal of Quantitative Spectroscopy and Radiative Transfer - Volume 112, Issue 14, September 2011, Pages 2335-2346