Electronic Structure, Molecular Interaction, and Stability of the CH4−nH2O Complex, for n = 1−21

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• 作者：Graciela Bravo-Pé ; rez ; Armando Cruz-Torres ; Ascenció ; n Romero-Martí ; nez
• 刊名：Journal of Physical Chemistry A
• 出版年：2008
• 出版时间：September 18, 2008
• 年：2008
• 卷：112
• 期：37
• 页码：8737-8751
• 全文大小：679K
• 年卷期：v.112,no.37(September 18, 2008)
• ISSN：1520-5215

文摘

Molecular calculations were carried out with four different methodologies to study the CH₄−nH₂O complex, for n = 1−21. The HF and MP2 methods used considered the O atom with pseudopotential to freeze the 1sd(0);" class="ref">(2) shell. The other methodologies applied the Bhandhlyp and B3lyp exchange and correlation functionals. The optimized CH₄−nH₂O structures are reported, specifying the number and type of H₂O subunits (triangle, square, pentagon, etc.) that comprised the nH₂O counterpart cluster or cage, that interacted with the CH₄ molecule, and, in the latter case, that provided its confinement. Results are focused to understand the stability of the CH₄−nH₂O complex. The quality of the electron correlation effect, as well as the size of the nH₂O cage to confine the guest molecule, and the number and type of H₂O subunits comprising the nH₂O cluster or cage are the most important factors to provide the stability of the complex and also dictate the particular n value at which the CH₄ molecule confinement occurs. This number was 14 for the HF, Bhandhlyp, and B3Lyp methods and 16 for the MP2 method. The reported hydrate structures for n < 20 could be predictive for future experiments.