河南南阳独山玉的岩相结构和无损分析(英文)

河南南阳独山玉的开采历史可以追溯到新石器时代,在我国玉文化中占有重要地位。鉴于当前对独山玉进行无损鉴别的方法较少,利用质子激发X荧光技术(proton induced X-ray emission,PIXE)、X射线衍射(X-ray diffraction,XRD)、激光Raman光谱(laser Raman spectroscopy,LRS)和扫描电子显微镜(scanning electron microscope,SEM)等技术对河南南阳独山玉料进行岩石矿物学分析。结果表明:独山玉主要由钙长石矿物构成,晶粒细小且结合紧密的显微结构与独山玉具有极高的稳定性有较大关系。PIXE,XRD和Raman技术作为无损分析方法为鉴定独山玉提供了准确有效的方法,为研究贵重的古玉样品提供了技术支持。

NCMAS系统熔体结构和动力学性质压力效应的分子动力学研究

Molecular dynamics simulations were used to study the pressure dependence of the structure and the dynamic properties of forsterite melt (Mg_2SiO_4), diopside melt (CaMgSi_2O_6), anorthite melt (CaAl_2Si_2O_8), jadite melt (NaAlSi_2O_6) and albite melt (NaAlSi3O8) from 0 GPa to 25 GPa at about 2000 K and the following conclusions have been reached. Firstly, the ratio of NBO to T (NBO and T denote the content of non-bridging oxygen and the total content of Si~(4+) and Al~(3+) respectively) is closely related to the pressure and the composition of the melts. It decreases monotonously in forsterite, diopside and anorthite melts while increases at the initial stage and then decreases in jadite and albite melts with increasing pressure. At a fixed pressure, the shear viscosity of the melts decreases with increasing NBO/T and the variation rate is almost 150 times higher in fully polymerized melts than that in de-polymerized melts in comparison with anorthite melts. Secondly, it is generally accepted that the formation of the Si and A1 will promote the diffusion of the network-forming ions. The hypothesis is frequently employed to explain the emergence of the maximum self-diffusion coefficient of the network-forming ions in fully polymerized melts. However, I detected that the pressure corresponding to the peak of the self-diffusion coefficient of the network-forming ions is lower than that corresponding to the maximum content of Si and A1, and that there exists an approximately linear relationship between the self-diffusion coefficient of the ions and the breaking frequency of the bonds under a given pressure, which is different from the present understanding about the mechanism of self-diffusion. Thirdly, the relationship between the self-diffusion coefficient of Si~(4+), Al~(3+) and O~(2-) and the shear viscosity of the melts evolves from the Stokes-Einstein equation and Sutherland-Einstein equation to the Eyring equation with increasing pressure. And the key to obtain self-diffusion coefficient from shear viscosity under difference pressures is to determine A. in the Eyring equation. For Si~(4+) and O~(2-), this could be done using the linear relationship between A, and NBO% in anorthite melts. However, this method is inapplicable in other kinds of melts.