A FUNDAMENTAL PARAMETERS APPROACH TO X-RAY LINE-PROFILE FITTING
A FUNDAMENTAL PARAMETERS APPROACH TO X-RAY LINE-PROFILE FITTING
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DOI：
10.1107/s0021889891010804
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发表时间：
1992-04-01
影响因子：
6.1
通讯作者：
COELHO, A
中科院分区：
文献类型：
--
作者：
CHEARY, RW;COELHO, A
本文提出了一种X射线粉末谱线轮廓拟合的卷积方法，其中谱线的形状由Cu K-α发射轮廓、衍射仪的尺寸和样品的物理变量综合而成。除了线轮廓的积分强度和2 θ位置之外，可以拟合的参数包括接收狭缝宽度、接收狭缝长度、X射线源尺寸、入射光束的发散角、样品的X射线衰减系数和微晶尺寸。这是一种自洽的拟合方法，因为仪器参数通常通过直接测量已知。为了最大限度地减少精密仪器参数之间的相关性，应同时拟合高2 θ值和低2 θ值的曲线。在这项工作中使用的铜K-α发射曲线是基于最近的单片双晶光谱仪测量，已经确定了在K-α-1和K-α-2组件的双峰结构。快速和准确的卷积程序已经开发和混合的多元线性回归和高斯-牛顿非线性最小二乘法与数值微分用于拟合的配置文件。该方法通过拟合结晶良好的MgO和Y3 Al 5 O 12（YAG）样品的粉末衍射数据进行评价。还通过检查在改变各种仪器参数（例如，接收狭缝宽度、检测器散焦、接收狭缝长度和包含单色器）之后拟合值的变化来进行测试。
A convolution approach to X-ray powder line-profile fitting is developed in which the line shape is synthesized from the Cu K-alpha emission profile, the dimensions of the diffractometer and the physical variables of the specimen. In addition to the integrated intensities and 2-theta positions of the line profiles, the parameters that may be fitted include the receiving-slit width, the receiving-slit length, the X-ray-source size, the angle of divergence of the incident beam, the X-ray attenuation coefficient of the specimen and the crystallite size. This is a self-consistent approach to fitting as the instrumental parameters are usually known by direct measurement. To minimize correlation between refined instrumental parameters, profiles at high and low 2-theta values should be fitted simultaneously. The Cu K-alpha emission profile used in this work is based on recent monolithic double-crystal spectrometer measurements that have identified a doublet structure in both the K-alpha-1 and K-alpha-2 components. Fast and accurate convolution procedures have been developed and a mixture of multilinear regression and Gauss-Newton non-linear least squares with numerical differentials is used for fitting the profiles. The method is evaluated by fitting powder diffraction data from well crystallized specimens of MgO and Y3Al5O12 (YAG). Testing has also been carried out by examining the changes in the fitted values after altering various instrumental parameters (e.g. receiving-slit width, detector defocus, receiving-slit length and inclusion of a monochromator).