Pathological crystal structures

Abstract

Recent decades have seen enormous changes in the technology of crystal structure analysis, but the interpretation of these data still depends on human judgment, and errors are far from uncommon. Although analysing the crystallographic results with available software tools can catch many types of errors, others can be detected only by combining the knowledge of both crystallography and chemistry. We discuss several such examples from the published literature, and for each of them we identify what lessons they teach us. The examples are categorized by the type of error: correct crystallography but incorrect chemistry, wrong identification of atoms, high-symmetry superstructures with included guest molecules, incorrect choice of space group, incorrect choice of unit-cell size, and unresolved problems. These examples are intended to counteract the aura of infallibility that crystal structures sometimes assume and to alert the reader to features to look for in detecting pathological structures.

Trendbericht Analytische Chemie 2024

“…49,50) Zusammenfassend ist in der Datenauswertung sehr viel in Bewe Diese Notwendigkeit verdeutlicht exemplarisch der kürzlich erschienene Artikel "Pathological crystal structures", der aus fehlerhaften Strukturbestimmungen aus der Literatur Schlüsse zieht und Lehrsätze formuliert. 52) Als Beispiel für eine nicht-triviale Strukturbestimmung zeigt der Artikel eine neue Phosphormodifikation, bei der die Daten eines sechsfach verzwillingten Kristalls gelöst und verfeinert wurden. 53) Demnach sind die 29 P 4 -Tetraeder analog der Struktur von α-Mn angeordnet.…”

Using Data from the Cambridge Structural Database to Practice Crystallographic Skills and Revise Erroneous Structures

“…Unfortunately, enforcement of this author instruction is not universal, and incorrect or incomplete structures sometimes end up in the literature. The recent paper by Raymond and Girolami, 6 and the references therein, provides an excellent description of the common errors in published structures. They present several case studies on issues such as misidentified atoms and issues with symmetry (space groups, unit cell selection, etc.)…”

Is a Crystal Structure Enough? Reflecting on the Reliability of SCXRD in the Age of Automation

“…The crystal structure appeared to be 5,5′-dichloro-2,2′-bipyridine. Encouragingly, checkCIF 10 gave only C level alerts, which meant the data set comfortably passed the quality standards for publication. We were surprised by this result, given that both our synthetic approach and all other typical characterization data indicated the structure to be incorrect.…”

“…These readily accessible resources must be critically scrutinized through expert peer-review and automated validation to legitimize their contribution. One of the most commonly employed verification methods for crystal structure data is the checkCIF routine of PLATON, which has been implemented in a web-based validation service by the International Union of Crystallography (IUCr). The checkCIF / PLATON validation consists of a vast array of individual tests covering many crystallographic statistics derived from the provided Crystallographic Information File (CIF).…”