Resolving the data ambiguity for periodic crystals and detecting (near-)duplicate structures

18^th August 2023, 14:00
Daniel Widdowson
MIF

Abstract

The most common definition of a crystal using a motif and unit cell is ambiguous since any crystal can be described by many different choices of motif and cell. We introduce our work on crystal descriptors which are ‘isometry invariants’ meaning any choice of motif and cell gives the same result. These invariants have mathematical properties that allow us to talk about individual crystals as being points in a ‘crystal space’ where the invariant acts as a coordinate, and geometrically similar crystals can be measured as such by simply comparing their coordinates. Fast comparisons between these invariants have enabled us to compare all crystals in the Cambridge Structural Database (CSD), Crystallography Open Database and Materials Project database to find geometrically identical or similar crystals. At least five examples in the CSD turned out to be worthy of investigation as data was potentially duplicated, but modified to avoid detection.