ProcessDiffraction VI.2: New possibilities in manipulating electron diffraction ring patterns

Abstract

<jats:p>A <jats:italic>free</jats:italic> computer program was introduced recently to process electron diffraction ring patterns. The program (called ProcessDiffraction) produces XDR-like output from the digitized version of the measured diffraction patterns. The enhanced functionality of V1.2 is summarized in the present paper.</jats:p><jats:p><jats:list list-type="number"><jats:list-item><jats:label>1.</jats:label><jats:p>The program starts with a hint-window giving suggestions what can be done next. Hints change permanently as processing progresses. The hint-window can be switched off optionally. It is a complement to the Windows-style Help-system.</jats:p></jats:list-item><jats:list-item><jats:label>2.</jats:label><jats:p>The center of the rings is found by manually shifting the measured pattern until it overlaps with a generated reference circle. The computer can further refine the position of the center.</jats:p></jats:list-item><jats:list-item><jats:label>3.</jats:label><jats:p>Elliptical distortion of the measured pattern (NOT of the display, which is irrelevant) is corrected by adjusting the eccentricity and axis direction of the reference ellipse (distorted from the reference circle) until visually coincide with the measured ring.</jats:p></jats:list-item></jats:list></jats:p>

Electron Diffraction Based Analysis of Phase Fractions and Texture in Nanocrystalline Thin Films, Part I: Principles

“…Other methods (Narayan, 1986; Hart, 2002) extract similar quantities off-line, from data, obtained either manually or by other processing programs (Hovmöller, 1992; Zou et al, 2004). The first versions of the popular 3 ProcessDiffraction program (Lábár, 2000, 2002, 2005; Lábár & Adamik, 2001) processed SAED patterns, but did not perform (semi)quantitative phase analysis. This article describes a method to determine the volume fraction of both randomly oriented and (specially oriented) textured crystalline phases in a nanocrystalline, thin TEM sample from its SAED pattern and the implementation of that method in the ProcessDiffraction program.…”

Electron powder diffraction

“…Preparation of the shortlist generally relies on a priori chemical information [obtained e.g. from energy-dispersive X-ray spectroscopy (EDS) or electron energy-loss spectrometry (EELS)] to reduce the number of candidate phases (crystalline structures) that are searched for (Lá bá r & Adamik, 2001; Lá bá r, 2006) in a comprehensive database such as the Powder Diffraction File (Faber & Fawcett, 2002). The identification of the crystalline phases in the experimental data is done through pattern fingerprinting.…”

Pattern Center and Distortion Determined from Faint, Diffuse Electron Diffraction Rings from Amorphous Materials

“…However, extraction of quantitative data from them is based on the accurate knowledge of the pattern center and the size and orientation of elliptical distortion. It is, therefore, not surprising that the last decade saw a continual effort to determine these parameters and correct for their effects (Lábár, 2000, 2002, 2005, 2008, 2009; Lábár & Adamik, 2001; Capitani et al, 2006; Li, 2007; Hou, 2008; Mitchell, 2008 a , 2008 b ; Carvalho & Morales, 2012; Wu et al, 2012; Klinger & Jager, 2015; Klinger et al, 2015; Mitchell & Van den Berg, 2016). Although all of them have their own success for solving part of the problem, some room was still left for improvement.…”

“…Mitchell (2008 b ) and Mitchell & Petersen (2012) offer four different approaches to obtain the first rough estimate, including simple or thresholding the patterns and a brute-force method. For manual determination of the first estimate of the pattern center (Lábár, 2000, 2002, 2005, 2008, 2009; Lábár & Adamik, 2001) offers visual comparison to a reference circle, while the pattern can be shifted until the symmetrically equivalent points are seen on the reference circle with variable radius. Mitchell (2008 b ) offers a similar manual possibility with several reference circles generated simultaneously on screen.…”

“…Klinger & Jager (2015) computes the difference between the original pattern and ones rotated around preassumed pattern center and minimize the difference by refining the center. Lábár (2000, 2002, 2008, 2009) and Lábár & Adamik (2001) determines both pattern center and elliptical distortion by manually overlaying a circle or an ellipse on the pattern and adjusting its parameters till good visual match is attained. Li (2007) computes intensity profiles both horizontally and vertically to obtain both pattern center and elliptical distortion.…”