Consistent indexing of a (set of) single crystal SAED pattern(s) with the ProcessDiffraction program

Research output: Contribution to journalArticle

197 Citations (Scopus)

Abstract

A computer program called "ProcessDiffraction" helps indexing a set of single crystal selected area electron diffraction (SAED) patterns by determining which of the presumed structures can fit all the measured patterns simultaneously. Distances and angles are measured in the digitalized patterns with a graphical tool by clicking on the two shortest non-collinear vectors (spots), using user-supplied calibration data. Centers of the spots and center of the pattern are optionally refined by the program. Suggested individual indexing solutions (consistent with an assumed unit cell) are listed by the program for each pattern. Simulated patterns are also consulted to check if the shortest calculated distances coincide with measured ones. Common solutions for the set are selected by checking the angles between the suggested zone axes against the angles between the experimental goniometer settings. The indexing process is manually controlled by selecting the candidate structures (one-by-one) for indexing and by specifying the tolerances for d-values, plane angles and zone angles. Patterns of any crystal system can be indexed successfully. Although error bars are larger in electron diffraction than in X-ray diffraction (XRD), frequently, many unrelated indexings are possible for any one electron diffraction pattern (irrespective of the indexing method), a set of SAED patterns can generally be indexed unambiguously, i.e. the three-dimensional reciprocal space can be identified correctly. Two other tools also help planning tilting experiments: zones along a plane can be listed (with their angles extended from a pre-selected zone in that plane) and zones lying at a given angle (specified with a tolerance) from a zone can also be identified (as they are situated between two cones). Another tool searches the XRD database directly either for advice on possible structures for a composition or to help calibration.

Original languageEnglish
Pages (from-to)237-249
Number of pages13
JournalUltramicroscopy
Volume103
Issue number3
DOIs
Publication statusPublished - Jun 2005

Fingerprint

Electron diffraction
Diffraction patterns
diffraction patterns
electron diffraction
Single crystals
single crystals
Calibration
Goniometers
X ray diffraction
Cones
Computer program listings
goniometers
Planning
Crystals
diffraction
planning
Chemical analysis
cones
x rays
computer programs

Keywords

  • Crystallography
  • Electron diffraction
  • Indexing
  • Tilting experiments

ASJC Scopus subject areas

  • Materials Science(all)
  • Instrumentation

Cite this

Consistent indexing of a (set of) single crystal SAED pattern(s) with the ProcessDiffraction program. / Lábár, J.

In: Ultramicroscopy, Vol. 103, No. 3, 06.2005, p. 237-249.

Research output: Contribution to journalArticle

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