Theoretical investigation for spectroscopic constants of ground-state alkaline-earth dimers with high accuracy |
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Authors: | Dong-Dong?Yang Email author" target="_blank">Fan?WangEmail author |
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Institution: | (1) College of Chemistry, Sichuan University, Chengdu, 610064, People’s Republic of China; |
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Abstract: | In this work, we provide highly accurate theoretical estimates for spectroscopic constants of the ground-state alkaline-earth
dimers (Ca2, Sr2, and Ba2). Electron correlation energies are calculated with coupled-cluster method at the single, double, and noniterative triple
excitations CCSD(T)] level, and the effects of full triples as well as quadruple excitations are also taken into account
at the CCSDT and the CCSDT(Q) level. Our results demonstrate that high-order electron correlation is important to achieve
results with high accuracy. We also find that results for Ca2 with counterpoise corrections, which are designed to eliminate the basis set superposition error, deviate further away from
those at the complete basis set limit than the uncorrected ones. The calculated binding energies and equilibrium bond lengths
for Ca2 and Sr2 are in excellent agreement with recent experimental data. On the other hand, our results for Ba2 are quite different from previous theoretical data, and there is no available experimental equilibrium bond length and binding
energy for calibration. Based on the performance of the adopted approach for Ca2 and Sr2, our results should be more reliable and could be helpful for future investigations. |
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