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本文通过B3LYP方法,在6-31G(d,p)水平下对结构Ⅰ型二氧化碳水合物的十二面体小晶穴和十四面体大晶穴的结构进行优化,并计算了其振动频率,~(13)C-NMR化学屏蔽常数及电子密度.结果表明,水合物晶穴的氢键键能强于水分子二聚体和冰晶格中的氢键键能.由此可以看出结构Ⅰ型二氧化碳水合物的晶穴是由氢键组成的稳定结构.通过CO_2分子与大、小晶穴的范德华能比较,发现CO_2分子在大晶穴中更稳定.所计算出的C=O键的不对称伸缩振动频率和~(13)C-NMR化学屏蔽常数与文献中的实验值基本一致.通过分析CO_2与晶穴的电子密度,其结果与氢键键能计算结果一致.计算结果还表明,CO_2在大晶穴中的稳定性较在小晶穴中的稳定性强.
In this paper, the structure of dodecahedron and tetradecahedron dacrystal structure of structure Ⅰ carbon dioxide hydrate was optimized by B3LYP method at 6-31G (d, p) level, and its vibrational frequency, ~ (13) C-NMR chemical shielding constant and electron density.The results show that the hydrogen bond of hydrate crystal lattice is stronger than that of water molecule dimer and ice crystal lattice. Type carbon dioxide hydrate is a stable structure composed of hydrogen bonds.Compared with van der Waals’ energy of CO 2 molecules and large and small spheres, we find that CO 2 molecules are more stable in large spar. The calculated C = O bonds The asymmetric stretching vibrational frequency and ~ (13) C-NMR chemical shielding constants are in good agreement with the experimental ones in the literature.The results are consistent with the hydrogen bond energy calculations by analyzing the electron density of CO_2 and the crystal lattice It shows that the stability of CO_2 in large crystal is stronger than that in small crystal.