The Convolutional Multiple Whole Profile (CMWP) Fitting Method, a Global Optimization Procedure for Microstructure Determination
The Convolutional Multiple Whole Profile (CMWP) Fitting Method, a Global Optimization Procedure for Microstructure Determination
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DOI：
10.3390/cryst10070623
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发表时间：
2020-07-01
期刊：
影响因子：
2.7
通讯作者：
Ungar, Tamas
中科院分区：
文献类型：
--
作者：
Ribarik, Gabor;Joni, Bertalan;Ungar, Tamas
利用基于完善的物理原理和晶格缺陷的透射电镜观察建立的谱线函数分析x射线和中子衍射图中的线展宽已被证明是表征晶体材料微观结构的有力工具。这些原理被应用于卷积多全剖面（CMWP）程序中，以确定位错密度、晶体尺寸、层错和孪晶界密度以及晶间应变。通过考虑应变各向异性、平面缺陷展宽和峰移的相关性以及缺陷相关的轮廓形状，分离了不同晶格缺陷对线展宽的贡献。只要衍射图相对简单，Levenberg-Marquardt （LM）峰拟合可以成功地确定晶体缺陷类型和密度。然而，在更复杂的情况下，如六边形材料或多相图案，单独使用LM程序可能会导致不确定性。在这里，我们扩展了CMWP过程，包括一个蒙特卡罗统计方法，其中LM和蒙特卡罗算法以交替的方式组合。更新后的CMWP程序消除了不确定性，并提供了与电子显微镜方法具有良好相关性的微结构全局优化参数。
The analysis of line broadening in X-ray and neutron diffraction patterns using profile functions constructed on the basis of well-established physical principles and TEM observations of lattice defects has proven to be a powerful tool for characterizing microstructures in crystalline materials. These principles are applied in the convolutional multiple-whole-profile (CMWP) procedure to determine dislocation densities, crystallite size, stacking fault and twin boundary densities, and intergranular strains. The different lattice defect contributions to line broadening are separated by considering thehkldependence of strain anisotropy, planar defect broadening and peak shifts, and the defect dependent profile shapes. The Levenberg-Marquardt (LM) peak fitting procedure can be used successfully to determine crystal defect types and densities as long as the diffraction patterns are relatively simple. However, in more complicated cases like hexagonal materials or multiple-phase patterns, using the LM procedure alone may cause uncertainties. Here, we extended the CMWP procedure by including a Monte Carlo statistical method where the LM and a Monte Carlo algorithm were combined in an alternating manner. The updated CMWP procedure eliminated uncertainties and provided global optimized parameters of the microstructure in good correlation with electron microscopy methods.