Use of electron backscatter diffraction patterns to determine the crystal lattice. Part 3. Pseudosymmetry

Area of Science:

• Crystallography
• Materials Science
• Electron Microscopy

Background:

• Electron backscatter diffraction (EBSD) patterns can lead to pseudosymmetric crystal lattice descriptions.
• Factors like limited pattern coverage, projection center inaccuracy, and Kikuchi band definition contribute to these errors.
• Inherent pseudosymmetries within crystal structures also complicate pattern analysis.

Purpose of the Study:

• To investigate the frequency and causes of pseudosymmetric crystal lattice descriptions from Kikuchi patterns.
• To quantify the impact of experimental and structural factors on EBSD data interpretation.
• To identify conditions leading to misinterpretations in crystallographic analysis.

Main Methods:

• Analysis of 350 simulated Kikuchi patterns using the CALM software.
• Systematic evaluation of factors influencing pattern symmetry and interpretation.
• Examination of atomic scattering factors and reciprocal lattice points for potential misinterpretations.

Main Results:

• Pseudosymmetry in crystal lattice descriptions is a notable issue in EBSD analysis.
• Misinterpretations are particularly frequent when atomic scattering factors are similar and reciprocal lattice points are systematically absent.
• A predictive model for pseudosymmetry in binary AB compounds (B1 and B2 structures) was developed.

Conclusions:

• Experimental limitations and inherent crystal symmetries are primary drivers of pseudosymmetric Kikuchi patterns.
• The study highlights the importance of careful analysis, especially concerning atomic scattering factors and lattice points.
• While useful for simple structures, the predictive approach is not directly applicable to complex phases.