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Updated: Jun 25, 2025
Microcrystallography of Protein Crystals and In Cellulo Diffraction
Published on: July 21, 2017
The importance of definitions in crystallography
Olga Anosova1, Vitaliy Kurlin1, Marjorie Senechal2
1Computer Science Department and Materials Innovation Factory, University of Liverpool, Liverpool, United Kingdom.
Abstract:
This paper was motivated by the articles `Same or different - that is the question' in CrystEngComm (July 2020) and `Change to the definition of a crystal' in the IUCr Newsletter (June 2021). Experimental approaches to crystal comparisons require rigorously defined classifications in crystallography and beyond. Since crystal structures are determined in a rigid form, their strongest equivalence in practice is rigid motion, which is a composition of translations and rotations in 3D space. Conventional representations based on reduced cells and standardizations theoretically distinguish all periodic crystals. However, all cell-based representations are inherently discontinuous under almost any atomic displacement that can arbitrarily scale up a reduced cell. Hence, comparison of millions of known structures in materials databases requires continuous distance metrics.
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