二氧化碳水合物小晶穴和大晶穴的密度泛函研究(英文)  

Density functional studies on small and large cavities of carbon dioxide hydrate

作　　者：温浩[1] 耿春宇[1,2] 

机构地区：[1]中国科学院过程工程研究所多相反应国家重点实验室,北京100190 [2]中国科学院研究生院,北京100049

出　　处：《计算机与应用化学》2008年第9期1171-1174,共4页Computers and Applied Chemistry

基　　金：the National Science Foundation of China (No．20221603)．

摘　　要：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.Geometry optimizations of type Ⅰ CO2 hydrate structure by B3LYP/6-31G（d,p） have been performed on CO2（H2O）20 and CO2（H20）24 clusters. Then the frequencies, 13C-NMR chemical shielding constants and electronic density are calculated. According to the results, the H-bond energies in each cavities are stronger than that in the water dimmer （H2O）2 and in hexagonal ice. Hence, both the cavities are stable units. The VDW interaction of CO2 with the large cavity is slightly stronger than that with the small cavity by considering the VDW interaction energy between CO2 and hydrogen-bonded water cavities. The calculated values of asymmetric C=O stretching frequencies and 13C-NMR chemical shieldings of the CO2 in the two clusters show good agreements with the experimental values in the references. Analysis of the electron density of CO2 and two cavities shows agreement with trends of OH…O hydrogen bonds and C=O bond lengths in two clusters. The calculated results also indicate that the stability for CO2 in the large cavity should be stronger than that in the small cavity, Key words： CO2 hydrate, B3LYP, stretching frequency, 13C-NMR chemical shieldings, electron density

关 键 词：CO2水合物 B3LYP 伸缩振动频率13C-NMR化学屏蔽常数 电子密度 

分 类 号：O6[理学—化学]