ELECTRON BACKSCATTER DIFFRACTION: NEW INDEXING METHODS TO UNDERSTAND CATION ORDERING

Monte-Carlo electron backscatter calculations coupled with high fidelity dynamical diffraction models have enabled generation of realistic simulated Electron Backscatter Diffraction (EBSD) patterns. These dynamically simulated EBSD patterns can be used in Forward Model-based indexing methods where experimental patterns are correlated against the simulations to achieve superior precision, excellent noise robustness, and the ability to resolve challenging problems. The methods expand the feasibility of EBSD analysis to extremely poor and noisy patterns on one side to high quality detailed patterns on the other side. Because these new indexing techniques use the full EBSD patterns, minute changes caused by small crystallographic differences such as cation ordering, complex pseudosymmetry problems, and solid solution/changing lattice parameters can now be identified and resolved.

The case study presented in this contribution focuses on the cation ordering in dolomite, which is of interest in understanding the origins of dolomite formation. Current approaches use XRD measurements to characterize that ordering. However, the experimental limitations of XRD based approaches may cause useful information, such as grain size or spatial relationships, to be lost or distorted as part of data collection/data reduction processes.

In this study, Dynamic Pattern Simulations have been utilized for a range of dolomite cation orderings to examine the feasibility of EBSD to be used as a tool to help understand the origins and properties of dolomite.