Effects on spectroscopic properties for several low-lying electronic states of CS molecule by core-valence correlation and relativistic corrections |
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Authors: | DH Shi WT Li XN Zhang JF Sun YF Liu ZL Zhu JM Wang |
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Institution: | College of Physics and Information Engineering, Henan Normal University, Xinxiang 453007, China |
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Abstract: | The potential energy curves (PECs) of six low-lying electronic states (X1Σ+, a3Π, a′3Σ+, d3Δ, e3Σ− and A1Π) of CS molecule have been investigated using the full valence complete active space self-consistent field (CASSCF) method followed by the highly accurate valence internally contracted multireference configuration interaction (MRCI) approach with large correlation-consistent basis sets. Effects on the PECs by the core-valence correlation and relativistic corrections have been taken into account. And the two corrections are performed at the level of cc-pV5Z basis set. The way to consider the relativistic corrections is to use the second-order Douglas-Kroll Hamiltonian approximation. Using the CCSD(T), MRCI and MRCI with the Davidson modification (MRCI + Q), the PECs of electronic states involved are extrapolated to the complete basis set (CBS) limit. With the PECs, the spectroscopic parameters (Te, Re, ωe, ωexe, ωeye, αe, βe, γe and Be) of the six low-lying electronic states are determined. These parameters are in excellent agreement with the experimental data. The complete vibrational states are computed for the six low-lying electronic states when the rotational quantum number J equals zero, and the inertial rotation constants of the first 23 vibrational states are reported, which agree favorably with the RKR data. Comparison with the measurements shows that the two-point total-energy extrapolation scheme can obviously improve the quality of spectroscopic parameters and molecular constants. |
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Keywords: | Potential energy curve Basis set extrapolation Spectroscopic parameter Size extensivity |
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