Nolze Gert, Tokarski Tomasz, Rychłowski Łukasz, Cios Grzegorz, Winkelmann Aimo
Federal Institute for Materials Research and Testing (BAM), Unter den Eichen 87, 12205 Berlin, Germany.
TU Bergakademie Freiberg, Institut für Mineralogie, Brennhausgasse 16, 09599 Freiberg, Germany.
J Appl Crystallogr. 2021 May 28;54(Pt 3):1012-1022. doi: 10.1107/S1600576721004210. eCollection 2021 Jun 1.
A new software is presented for the determination of crystal lattice parameters from the positions and widths of Kikuchi bands in a diffraction pattern. Starting with a single wide-angle Kikuchi pattern of arbitrary resolution and unknown phase, the traces of all visibly diffracting lattice planes are manually derived from four initial Kikuchi band traces via an intuitive graphical user interface. A single Kikuchi bandwidth is then used as reference to scale all reciprocal lattice point distances. Kikuchi band detection, via a filtered Funk transformation, and simultaneous display of the band intensity profile helps users to select band positions and widths. Bandwidths are calculated using the first derivative of the band profiles as excess-deficiency effects have minimal influence. From the reciprocal lattice, the metrics of possible Bravais lattice types are derived for all crystal systems. The measured lattice parameters achieve a precision of <1%, even for good quality Kikuchi diffraction patterns of 400 × 300 pixels. This band-edge detection approach has been validated on several hundred experimental diffraction patterns from phases of different symmetries and random orientations. It produces a systematic lattice parameter offset of up to ±4%, which appears to scale with the mean atomic number or the backscatter coefficient.
本文介绍了一种新软件，用于根据衍射图样中菊池带的位置和宽度来确定晶格参数。从具有任意分辨率和未知相位的单个广角菊池图样开始，通过直观的图形用户界面，从四条初始菊池带迹线手动得出所有可见衍射晶格平面的迹线。然后使用单个菊池带的宽度作为参考来缩放所有倒易点阵点的距离。通过滤波后的芬克变换进行菊池带检测，并同时显示带强度分布，有助于用户选择带的位置和宽度。由于过剩 - 不足效应影响极小，因此使用带轮廓的一阶导数来计算带宽。从倒易点阵中，为所有晶体系统推导可能的布拉菲晶格类型的度量。即使对于400×300像素的高质量菊池衍射图样，所测量的晶格参数精度也能达到<1%。这种带边检测方法已在数百个来自不同对称性和随机取向相的实验衍射图样上得到验证。它会产生高达±4%的系统晶格参数偏移，该偏移似乎与平均原子序数或背散射系数成比例。
