Study on the crystal structure of deep sections of Antarctic ice cores

用拉曼光谱和非相干非弹性中子谱观测到了南极冰芯的特征，认为这是由于冰结构中的质子有序化所致。为了阐明南极冰芯的晶体结构特征，本研究主要利用X射线衍射仪对南极冰芯的晶体结构进行了研究。(1)冰晶结构的X射线衍射研究对Vostok冰芯的深部进行了X射线摇摆曲线测量，根据剖面的宽度确定了位错密度。随着深度的增加，位错密度从10^&lt；12；m；-2；-2；减小到10^-8m；-2&gt；随着深度的增加，位错密度降低。在最深的部位，位错密度较低，这是因为冰层是由Vostok湖水长期冻结形成的。(2)晶体结构的X射线粉末衍射研究…的(1121)面反射更多的是有序冰的特征(冰XI)在任何样品中都很少观察到。这是因为这种反射的强度预计会很低，因此，在进一步的研究中需要像同步辐射这样的强X射线源。(3)用X射线粉末衍射法测定了冰芯样品的点阵常数。冰芯样品的晶格常数大于实验室冰样的晶格常数，并随着深度的增加而增大，但由于残余应力的影响，晶格常数预计会较小。变形冰的拉曼光谱为了揭示已报道的南极冰特征光谱的来源，测量了变形冰的拉曼光谱。然而，没有观察到明显的变化。因此，南极冰盖中冰的变形不是产生特征光谱的可能原因。(5)笼状水合物的形成过程和冰晶结构分子动力学模拟揭示了笼状水合物形成过程中冰中气体扩散的新机制。我们首先发现，在扩散过程中，气体形成了一种特征的中间结构，打破了一对水分子之间的氢键。较少

Characteristic features in Antarctic ice cores have been observed by Raman and incoherent inelastic neutron spectra, which have been attributed to proton ordering in ice structure. In this study, to elucidate the characteristic crystal structure of ice cores from Antarctica were investigated mainly by X-ray diffraction. The followings are the results in this research:(1) X-ray diffraction study of structure of ice crystalX-ray rocking curve measurements were conducted for deep sections of Vostok ice core and the dislocation density was determined from the width of the profiles. The dislocation density decreases from 10^<12>m^<-2> to 10^8 m^<-2>, as depth increases between 3200 and 3611 m. The dislocation density was lower in deepest sections because^the ice was formed by the refreezing of Vostok Lake water in a long period.(2) X-ray powder diffraction study of crystal structureThe observed profiles by X-ray powder diffraction did show sample or depth dependency. The (1121) reflection w … More hich is characteristic of ordered ice (ice XI) was scarcely observed in any samples. This is because the intensity of this reflection is expected to be very low and, therefore, strong X-ray source like synchrotron radiation is necessary in a further study. X-ray diffuse scattering measurements are also important in the further study.(3) Lattice constants determined by X-ray powder diffractionLattice constants of ice core samples were determined by Reidtveld analysis of X-ray powder diffraction profiles. The lattice constants of ice core samples are larger than that of laboratory ice and increase with the depth although they are expected to be smaller due to residual stress. The origin of this behavior should be investigated in a further study.(4) Raman Spectra of deformed iceTo reveal the origin of the reported characteristic spectra of Antarctic ice, Raman spectra for deformed ice were measured. However, no significant change was observed. Thus, the deformation of ice in the Antarctic ice sheet is not a possible reason for the characteristic spectra.(5) Formation process of clathrate hydrate and ice crystal structureMolecular dynamics simulations elucidated a new diffusion mechanism of gases in ice during clathrate hydrate formation from ice. We first found that in the diffusion process gas forms a characteristic intermediate structure breaking a hydrogen bond between a pair of water molecules. Less