权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Studies on the Phonon Dynamics and Structural Phase Transitions in Clathrate Hydrates by Raman and X-ray Scattering

拉曼和X射线散射研究笼形水合物中的声子动力学和结构相变

基本信息

批准号：
06640668
负责人：
WADA Noboru
金额：
$ 1.34万
依托单位：
Toyo University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06640668/
关键词：
Clathrate Hydrate Raman Scattering X-ray Diffraction フラロール

项目摘要

The purpose of this research is to study the phonon dynamics and structural phase transitions in clathrate hydrates. In particular, we are interested in the changes of the hydrogen bonds of water molecules upon the transitions and the molecular field around the guest molecule.First, water solusion of fullerol C_<60> (OH) _X is studied. The solution is found, however, to contain some chemical impurities such as NaOH and tetrabutylammoniumhydroxide. Though, at this time, we are not successful in completely characterizing the samples, we hope to purify C_<60> (OH) _X and conduct more quantitative experiments on the fullerol clathrate hydrate system.Second, tetrahydrofuran (THF) clathrate hydrate and liquid THF・17H_2O are studied by Raman spectroscopy. From the frequencies of O-H vibrations as well as the hydrogen bond vibrations, we suggest that the strength of the H_2O host network in liquid THF・17H_2O is about the same as that in water. Upon the formation of the hydrate, the H_2O host network becomes stronger. The frequencies of the C-O-C and CH_2 vibrations of THF molecules in THF hydrate are found to be higher than in pure THF liquid. The depolarization ratios of the C-O-C symmetric and asymmetric stretching vibrations vary drastically as the THF molecules are in different physical states, such as in pure THF liquid, in liquid water, and in the cages of the hydrate. We suggest that THF molecule in THF hydrate is more like a free THF molecule in the gas phase, in which the five-member ring of THF molecule is buckled. The five-member ring of THF molecule is more planar when THF is liquid THF・17H_2O.An Ag-like mode at 900cm^<-1>, which is not observable in either pure water or pure THF liquid, is observed in the Raman spectra of liquid THF・17H_2O and THF hydrate.

本文主要研究笼形水合物的声子动力学和结构相变。特别地，我们对水分子的氢键在跃迁过程中的变化以及客体分子周围的分子场感兴趣。首先，研究了富勒醇C_<60>（OH）_X的水溶液。然而，发现该溶液含有一些化学杂质，如NaOH和四丁基氢氧化铵。虽然目前我们还不能完全表征样品，但我们希望能对<60>富勒醇笼形水合物体系的C_（OH）_X进行纯化，并对富勒醇笼形水合物体系进行更多的定量实验。其次，对四氢呋喃（THF）笼形水合物和液体THF·17H_2O进行了拉曼光谱研究。从O-H振动和氢键振动的频率，我们认为在液体THF·17H_2O中H_2O主体网络的强度与在水中的强度大致相同。水合物形成后，H_2O主体网络变得更强。发现THF水合物中THF分子的C-O-C和CH_2振动频率比纯THF液体中的高。当THF分子处于不同的物理状态（如在纯THF液体中、在液态水中和在水合物的笼中）时，C-O-C对称和不对称伸缩振动的退极化比变化剧烈。我们认为THF水合物中的THF分子更像是气相中的自由THF分子，THF分子的五元环在其中发生了屈曲。当THF为液态THF·17 H_2O时，THF分子的五元环更加平坦。<-1>在液态THF·17 H_2O和THF水合物的拉曼光谱中，观察到在900 cm ~ 2处的类银模式，这在纯水和纯THF液体中都没有观察到。