Tsubota Masami, Kitagawa Jiro
Physonit Inc., 6-10 Minami-horikawa, Kaita, Aki, Hiroshima, 736-0044, Japan.
Department of Electrical Engineering, Faculty of Engineering, Fukuoka Institute of Technology, 3-30-1 Wajiro-higashi, Higashi-ku, Fukuoka, 811-0295, Japan.
Sci Rep. 2017 Nov 13;7(1):15381. doi: 10.1038/s41598-017-15766-y.
To obtain the lattice parameters accurately by the Rietveld method, the relationship between the lattice parameters and the peak-shift, which is the deviation in diffraction angle from the theoretical Bragg position, was studied. We show that the fitting accuracy of lattice parameters is related directly to the well reproducibility of the peak-shift. This study unveils that the peak-shift consists of the experimental and the analytical ones. The analytical peak-shift erroneously lowers a reliability factor R , which has, so far, been the conventional criterion of fit. The conventional Rietveld method obtains a unit-cell which is a homothetic (proportional) unit-cell of the true one. We propose an additional criterion based on the peak-shift to obtain the true lattice parameters accurately. Our criterion can achieve reproducibility reasonably well for the experimental peak-shift, leading to highly improved accuracy of the lattice parameters.
为了通过Rietveld方法准确获得晶格参数，研究了晶格参数与峰移之间的关系，峰移是衍射角相对于理论布拉格位置的偏差。我们表明，晶格参数的拟合精度直接与峰移的良好可重复性相关。本研究揭示，峰移由实验峰移和分析峰移组成。分析峰移错误地降低了可靠性因子R，而R迄今为止一直是传统的拟合标准。传统的Rietveld方法得到的晶胞是真实晶胞的相似（成比例）晶胞。我们提出了一种基于峰移的附加标准，以准确获得真实的晶格参数。我们的标准可以合理地实现实验峰移的良好可重复性，从而大大提高晶格参数的精度。
