To understand the initial hydration processes of CaCl2, we performed molecular simulations employing the force field based on the theory of electronic continuum correction with rescaling. Integrated tempering sampling molecular dynamics were combined with ab initio calculations to overcome the sampling challenge in cluster structure search and refinement. The calculated vertical detachment energies of CaCl2(H2O)n− (n = 0–8) were compared with the values obtained from photoelectron spectra, and consistency was found between the experiment and computation. Separation of the Cl—Ca ion pair is investigated in CaCl2(H2O)n− anions, where the first Ca—Cl ionic bond required 4 water molecules, and both Ca—Cl bonds are broken when the number of water molecules is larger than 7. For neutral CaCl2(H2O)n clusters, breaking of the first Ca—Cl bond starts at n = 5, and 8 water molecules are not enough to separate the two ion pairs. Comparing with the observations on magnesium chloride, it shows that separating one ion pair in CaCl2(H2O)n requires fewer water molecules than those for MgCl2(H2O)n. Coincidentally, the solubility of calcium chloride is higher than that of magnesium chloride in bulk solutions.
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14 June 2018
Research Article|
May 30 2018
Molecular dynamics simulation, ab initio calculation, and size-selected anion photoelectron spectroscopy study of initial hydration processes of calcium chloride
Special Collection:
Ions in Water
Zhili He;
Zhili He
a)
1
Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University
, Beijing 100871, China
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Gang Feng
;
Gang Feng
a)
2
Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences
, Beijing 100190, China
3
School of Chemistry and Chemical Engineering, Chongqing University
, Chongqing 401331, China
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Bin Yang;
Bin Yang
2
Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences
, Beijing 100190, China
4
University of Chinese Academy of Sciences
, Beijing 100049, China
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Lijiang Yang;
Lijiang Yang
1
Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University
, Beijing 100871, China
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Cheng-Wen Liu;
Cheng-Wen Liu
1
Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University
, Beijing 100871, China
5
Department of Biomedical Engineering, The University of Texas at Austin
, Austin, Texas 78712, USA
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Hong-Guang Xu
;
Hong-Guang Xu
2
Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences
, Beijing 100190, China
4
University of Chinese Academy of Sciences
, Beijing 100049, China
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Xi-Ling Xu
;
Xi-Ling Xu
2
Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences
, Beijing 100190, China
4
University of Chinese Academy of Sciences
, Beijing 100049, China
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Wei-Jun Zheng
;
Wei-Jun Zheng
b)
2
Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences
, Beijing 100190, China
4
University of Chinese Academy of Sciences
, Beijing 100049, China
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Yi Qin Gao
Yi Qin Gao
b)
1
Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University
, Beijing 100871, China
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a)
Z. He and G. Feng contributed equally to this work.
b)
Electronic addresses: zhengwj@iccas.ac.cn and gaoyq@pku.edu.cn
J. Chem. Phys. 148, 222839 (2018)
Article history
Received:
January 31 2018
Accepted:
May 09 2018
Citation
Zhili He, Gang Feng, Bin Yang, Lijiang Yang, Cheng-Wen Liu, Hong-Guang Xu, Xi-Ling Xu, Wei-Jun Zheng, Yi Qin Gao; Molecular dynamics simulation, ab initio calculation, and size-selected anion photoelectron spectroscopy study of initial hydration processes of calcium chloride. J. Chem. Phys. 14 June 2018; 148 (22): 222839. https://doi.org/10.1063/1.5024279
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