再论粉末法测低对称的晶胞参数

1980—1981年,作者曾提出用修正指标化结合加权最小二乘拟合,利用X射线粉末图计算低对称晶胞参数的方法;在这篇文章中,作者又提出一个用叠代地修正测定值代替修正指标化的改进方法,来处理上述问题。该方法已用BASIC语言编写出程序,并在CROMEMCO—S—Ⅲ型微机上成功地运行。实践表明,改进的方法提高了测定精度,效果良好。     

粉晶X射线衍射理论计算和CIF数据转换软件—XRAY

本文简要介绍一个进行粉晶X射线理论计算和CIF文件转换的计算机软件-XRAY，其输入内容仅要求X射线波长，晶胞参数，空间群和原子坐标等，输出内容包括衍射图谱的图形方式和一个包含2θ、d值、相对强度和指标化的列表，并可进行CIF文件的输出转换，它可作为科学研究的辅助工具以及用于X射线结晶学的数学演示。     

单斜辉石的 X 射线粉末法研究

辉石是最重要的造岩矿物之一。无论是研究火成岩,变质岩,还是研究深部地质或月球岩石都离不开辉石的鉴定和研究。在工艺岩石学(例如铸石学)的研究中辉石鉴定问题也极为重要,尤其是X射线粉末法鉴定。因此,近五十年来很多人对辉石的X射线粉末图进行过研究。为了研究辉石类质同象对晶格常数的影响及其和成因的关系,各种辉石(主     

纪尼叶聚焦相机——一种提高分辨率的衍射装置

X射线粉末衍射法已有很长的历史。在近十至十五年内,计算机应用的结果,使得粉末法在粉末图谱指标化和晶胞参数精细测定等方面均有较大的进展,可以取得更多更深的结构信息。粉末数据现代计算方法的基础是粉末图谱的分辨率和衍射角测量的精确度。怎样获得高质量的粉末数据?采用纪尼叶聚焦照相技术看来是一种很好的手段。     

一维非公度调制结构安康矿X射线衍射及四维空间指标化研究

采用最新的CCD单晶衍射仪,对一维非公度调制结构矿物安康矿进行了单晶和粉晶X射线衍射研究,利用单晶X射线衍射和三维超结构分析方法测定晶胞参数a=1.014 08(10)nm,b=1.014 08(10)nm,c=0.295 72(6)nm,α=90,°=β90,°γ=90,°调制向量q=0.444c*,据此对单晶衍射数据进行了四维空间的指标化。并用新近研究开发的利用单晶体来进行粉晶衍射的新方法对粉晶衍射实验及粉晶数据的四维空间进行指标化研究。     

坡缕石精细鉴定的粉末X射线衍射法

对安徽官山两个含镁量不同的坡缕石进行了粉末X射线衍射(XRD)分析,结果表明其中富镁者为正交晶系、贫镁者为单斜晶系矿物,细化了判别坡缕石晶系的X射线粉末衍射标志。在排除石英和蒙脱石或伊利石的影响后,若图谱中出现d值为0.446 nm和0.428 nm的衍射线,则可认为在该凹凸棒粘土中含有正交晶系坡缕石。晶胞参数计算结果亦表明富镁坡缕石为一正交晶系坡缕石,贫镁坡缕石为一单斜晶系坡缕石。     

使用Q函数求解低对称晶系矿物晶胞参数的叠代修正法

本文提出一种使用Q函数求解低对称晶系矿物晶胞参数的叠代修正法。根据抛弃法数据处理原理,从粉末衍射图谱的低角区到高角区不断地重复精化晶胞参数与扩大指标化两步骤,利用△Q及|1-ρ|作为判别函数,用ALGOL 60语言编写了计算机程序,计算结果表明这方法是可行的。     

单色光源X光机在改进粉末图谱精确度和清晰度中的作用

在近10—15年内,由于计算方法的发展,使得粉末法在获得精确的晶胞参数、正确地指标化粉末图谱及取得结构信息等方面均有较大的突破。粉末数据现代计算分析方法的基础与计算机自动检索卡片成功率,都取决于粉末图谱的分辨率、探测限(两者与粉末谱的清晰度有关),以及衍射角测量的精确度。X射线粉末衍射仪只要分辨率和背景值都能调到最佳状态,是能满足要求的。但对衍射仪的零点调节、校正及记录方式都要求极严。快速扫描通常不能达到这样的水平,而需慢速阶梯扫描。高精度的数据系统误差要求在±0.02°(2θ)范围内。本文将介绍一种采用单色X射线源的实验手段及其测量校正计算方法,相对来说是比较快速和行之有效的,可起到提高粉末图谱的清晰度与精确度的作用。     

福建紫金山铜金矿床中的完整Cu-S体系矿物

在电子探针微区化学成分分析的基础上,结合 X 射线粉末衍射分析,对福建紫金山铜金矿床中的 Cu-S 体系矿物进行 了化学成分和晶体结构特征的研究。结果在该矿床中发现较完整的 Cu-S 体系矿物系列,包括铜蓝、雅硫铜矿、斯硫铜矿、 吉硫铜矿、斜方蓝辉铜矿、蓝辉铜矿、久辉铜矿和辉铜矿。此外,利用粉末 X 射线衍射数据,计算了铜蓝、斜方蓝辉铜矿、 蓝辉铜矿、久辉铜矿、辉铜矿等五种矿物的晶胞参数。基于系统矿物学的研究,建立了紫金山铜金矿床 Cu-S 体系完整矿物 的结晶与变化序列,该工作在国内尚属首次,同时也丰富了 Cu-S 体系矿物基础矿物学研究的资料。     

岩石矿物数据处理微型计算机软件系统研制

微型计算机是国际上近年来迅速发展起来的一个重要分支,它具有价廉、方便、体积小、多效能等优点,正在向各个领域普及。在岩石学、矿物学研究领域中,随着科学技术的发展和研究工作的深入,能获得的数据越来越多,数据处理量也越来越大。有的数据处理特别繁琐,要花费大量时间,比如标准矿物分子计算法,有的是手算无法进行的,如三斜晶系的晶胞参数修正。1983年,作者利用美国Cromemco Ⅱ微型计算机,研制成功岩石矿物数据处理微型计算机软件系统(PM-C2系统),这个系统包括岩石化学、矿物分子式、温度压力、晶胞参数修正等程序。     

Structural investigations of polycrystalline diaspore samples by X-ray powder diffraction

Diaspore (α-AlOOH) samples of different origin have been investigated by means of X-ray powder diffraction. Film and diffractometer data, evaluated by common least squares and least squares profile-fitting refinement methods, respectively resulted in the same values of structural parameters. The structural invariability of natural diaspores can be concluded from the results.     

An alkali feldspar series

A series of single-phase alkali feldspars in the system Na₂O-K₂O-Al₂O₃-SiO₂-H₂O were crystallized from dehydrated gels at 500 bars and 800° C, in the presence of an aqueous vapor phase, quartz, and corundum. Twenty of these bulk samples were analyzed for K₂O and Na₂O by atomic absorption spectrophotometry. The unit cell parameters for 19 of these samples and 8 others in the series were obtained by least squares refinement of x-ray powder diffraction data collected with a focusing camera. Polynomial expressions giving the variation in unit cell parameters as a function of composition, in mol fraction potassium feldspar, were obtained, and compared with similar polynomial expressions developed from the avilable data on the sanidine-high albite series.This series of alkali feldspars is distinct from the previously studied series, but is closely related to the sanidine-high albite series. The differences illustrated by this series are principally in the higher values of the b and c unit cell edges, for a given N_or, and consequently higher unit cell or molar volume for a given N_or.Although the source of these differences may be related to crystalline solution with a hydronium (or oxonium) feldspar molecule, H₃OAlSi₃O₈, a more probable source of these differences is that this feldspar series is less ordered in terms of Al/Si distribution than the sanidine-high albite series.     

Neutron diffraction determination of the cell dimensions and thermal expansion of the fluoroperovskite KMgF3 from 293 to 3.6 K

The cell dimensions of the fluoroperovskite KMgF₃ synthesized by solid state methods have been determined by powder neutron diffraction and Rietveld refinement over the temperature range 293–3.6 K using Pt metal as an internal standard for calibration of the neutron wavelength. These data demonstrate conclusively that cubic $ Pm\overline{3} m The cell dimensions of the fluoroperovskite KMgF₃ synthesized by solid state methods have been determined by powder neutron diffraction and Rietveld refinement over the temperature range 293–3.6 K using Pt metal as an internal standard for calibration of the neutron wavelength. These data demonstrate conclusively that cubic KMgF₃ does not undergo any phase transitions to structures of lower symmetry with decreasing temperature. Cell dimensions range from 3.9924(2) ? at 293 K to 3.9800(2) ? at 3.6 K, and are essentially constant within experimental error from 50 to 3.6 K. The thermal expansion data are described using a fourth order polynomial function.     

A neutron diffraction study of alkali cation migration in montmorillonites

Neutron powder diffraction measurements on lithium and cesium saturated montmorillonite samples before and after heat treatment at 300°C are studied, in order to undertake a complete refinement of crystal structure and unravel the migration mechanism for the interlayer cations of Li or Cs. Rietveld analysis of the corresponding diffraction patterns finds that montmorillonite crystallizes in the C2/m space group with unit cell dimensions consistent with the size of the specific interlayer cation. We show that thermal treatment affects the two types of samples in a different way. This is with respect to their unit cell dimensions and the migration of Li from the 2b to the 2c clay lattice site, in constrast to the Cs positioning which remains effectively unchanged.     

晶体点阵参数最小二乘法计算程序

作者以最小二乘法理法导出了晶体点阵参数计算的公式,并顾及了X射线粉晶衍射图测定所引起的系统误差修正,从而得到点阵参数的最佳估值。以导出的公式为数学模型编制了PC-1500微机的扩展BASIC语言程序,可适用于各晶系点阵参数的计算,使用方便。     

关于新矿物“等轴铂铜矿”与红石矿的进一步讨论

1974年于祖相等同志著文报导,在我国某地含铂岩体中发现了红石矿这一铂族新矿物,该矿物不久得到国际新矿物委员会的通过。1976年红石同志在地球化学上发表了产在同一地区的另一新矿物,即等轴铂铜矿。从两篇文章来看,这两种矿物的化学成分及物理性质颇为相近,但前者被定为六方晶系,而后者为等轴晶系,所求得的晶胞参数更是大不相同。对此,国内一些矿物工作者曾提出一些疑问。为了弄清这一问题,我们除对上述矿物所有资料进行认真对比和分析外,又补做了一些实验研究,认为此两种矿物完全属于同一矿物。以下简要地报导我们的分析结果及看法,以资进一步商榷。     

约束最小二乘法优选单位线

在总结目前推求单位线方法的基础上,提出了一种改进的优化方法－－约束最小二乘法。它通过Ｗｉｎｄｏｗｓ平台上的可视化编程,不震拟定初始单位线和试错,就能快速准确达到单位线的最优适配,并能够在计算机上实现推求和修匀单位线。     

Exploration of structure and bonding in stishovite with fourier and pseudoatom refinement methods using single crystal and powder X-ray diffraction data

The structure and bonding in stishovite, SiO₂, is explored with Fourier summation and pseudoatom refinement of merged x-ray single crystal and powder diffraction data. Replacement of the 25 lowest-angle, highly extinction-affected, single crystal reflections with structure factors obtained from low-extinction powder diffraction data has resulted in a significant improvement in the analysis compared with earlier studies. The deformation electron density, total electrostatic potential and total and valence electron densities are mapped. Accumulations of electron density are observed in both SiO bonds, together with non-bonding features displayed about the oxygen on both sides of a plane formed by three bonds with Si. Deficits of electron density between O atoms across the shared-edges are rationalized in terms of the Pauli exclusion principle. There is no evidence for strong repulsion of Si atoms across the same ring. The total electrostatic potential has a continuous low value for the vacant channels in the structure along c with localized minima between O atoms on opposite sides of the channel. The sizes of Si and O are related to the electron density and to the electrostatic potential.