Quantification of Polycrystalline Electron Diffraction Pattern

(QPCED v2.5)

X.Z. Li

Polycrystalline electron diffraction is a complementary technique to powder X-ray diffraction for structural analysis. The polycrystalline electron diffraction is considered a very important analytical tool in the study in nano materials e.g. ultra thin film and nano particles.

QPCED2.5 is a Java software for digitization, processing and quantification of polycrystalline electron diffraction patterns. This is an essential step for quantitative (semi-quantitative) analysis, e.g., phase identification, lattice parameter refinement, texture measurement, phase component estimation in multi-phase system, and structure determination for unknown phases. The QPCED2.5 is self-contained software and can also used together with the PCED2.0 [1], which is developed for the simulation of polycrystalline electron diffraction pattern.

The first version of QPCED was developed in 2006, two Java programs were written, one for digitizing the polycrystalline electron diffraction pattern and the other for quantifying the digitized diffraction profile. The work was published in the microscopy and microanalysis meeting 2007 [2] but used mainly in the authorīs home institution [3]. QPCED2.0 was written in 2010, the functions of the original QPCED are greatly enhanced and extended. The original two programs were merged into one under a common GUI, the work will be published in the microscopy and microanalysis meeting 2011[4]. QPCED2.0 has been further improved based on user's feedback, including pattern enhancement for weak diffraction patterns. Current version is QPCED2.5. The graphic user interface (GUI) is greatly improved in the new version.

Some screen shots of the QPCED2.5 are given below.

Figure 2. (a) an original ED pattern, (b) the ED pattern in inverted palette, (c) the ED pattern in blackbody palette and (d) the ED pattern with max intensity profile and highlighted marks.

Figure 3. (a) A pseudo-colored polycrystalline diffraction pattern from a fiber using rainbow palette, (b) the original diffraction pattern with selected band indicated by two thin red circles. (c) the integral intensity profile of the selected band.

Figure 4. (a) The area of the incident beam is defined before converting a pattern profile, (b) the pattern profile with the incident beam peak removed, and (c) the profile conversion panel.

Figure 5. (a) A pattern profile with a background curve and the profile analysis panel.

Figure 6. Refinement of a list of peaks to fit the pattern profile (above) and the difference between the two curves (below).

Figure 7. Diagram and table of the peaks after refinement. The table shows a list of peaks in position, height, d-spacing and normalized integral intensity.

References

[1] X.Z. Li. PCED2.0 - A Computer Program for Advanced Simulation of Polycrystalline Electron Diffraction Pattern, Ultramicroscopy, 110, 297 (2010).
[2] X.Z. Li. Quantitative Analysis of Polycrystalline Electron Diffraction Patterns, Proceeding of Microscopy and Microanalysis 2007 (Fort Lauderdale, Floriada, Auguest 5-9). Edited by M. Marko et al. Microsc Microanal 13(Suppl 2), 966 CD.
[3] e.g. X.Z. Li, X.H. Wei, R. Skomski, and D.J. Sellmyer. Structure and Magnetism of Co:CoO Core-shell Nanoclusters, Journal of Nanoparticle Research, 12, 789 (2010).
[4] X.Z. Li. Processing and Quantification of Polycrystalline Electron Diffraction Patterns, Proceeding of Microscopy and Microanalysis 2011 (Nashville, Tennessee, Auguest 7-11).
[5] Landyne Software is a company registered by X.Z. Li and Z.Y. Yang in Nebraska. E-mail address: landy_ne@yahoo.com or xli2@unl.edu.
[6] S. Bruechner. Estimation of the background in powder diffraction patterns through a robust smoothing procedure, J. Appl. Cryst. 33, 977 (2000).