New similarity index for crystal structure determination from X-ray powder diagrams

2005 ◽  
Vol 38 (6) ◽  
pp. 861-866 ◽  
Author(s):  
Detlef Walter Maria Hofmann ◽  
Ludmila Kuleshova
Keyword(s):  
Crystal Structure ◽  
Structure Determination ◽  
Structure Prediction ◽  
Similarity Index ◽  
Crystal Structure Determination ◽  
Crystal Structure Prediction ◽  
X Ray ◽  
Organic Pigments ◽  
Structure Solution ◽  
Similarity Indices

A new similarity index for automated comparison of powder diagrams is proposed. In contrast to traditionally used similarity indices, the proposed method is valid in cases of large deviations in the cell constants. The refinement according to this index closes the gap between crystal structure prediction and automated crystal structure determination. The opportunities of the new procedure have been demonstrated by crystal structure solution of un-indexed powder diagrams of some organic pigments (PY111, PR181 and Me-PR170).

Crystal structure determination by combined synchrotronpowder X-ray diffraction and crystal structure prediction: 1 : 1 l-ephedrined-tartrate

CrystEngComm ◽  
2013 ◽  
Vol 15 (10) ◽  
pp. 1853-1859 ◽  
Author(s):  
Han Wu ◽  
Matthew Habgood ◽  
Julia E. Parker ◽  
Nik Reeves-McLaren ◽  
Jeremy K. Cockcroft ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Structure Determination ◽  
Structure Prediction ◽  
Crystal Structure Determination ◽  
Crystal Structure Prediction ◽  
X Ray Diffraction ◽  
X Ray

scholarly journals Crystal structures of two furazidin polymorphs revealed by a joint effort of crystal structure prediction and NMR crystallography

2020 ◽  
Vol 76 (3) ◽  
pp. 322-335 ◽  
Author(s):  
Marta K. Dudek ◽  
Piotr Paluch ◽  
Edyta Pindelska
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Structure Determination ◽  
Structure Prediction ◽  
Structural Features ◽  
Crystal Structure Determination ◽  
Crystal Structure Prediction ◽  
Crystal Forms ◽  
Space Groups ◽  
Nmr Crystallography

This work presents the crystal structure determination of two elusive polymorphs of furazidin, an antibacterial agent, employing a combination of crystal structure prediction (CSP) calculations and an NMR crystallography approach. Two previously uncharacterized neat crystal forms, one of which has two symmetry-independent molecules (form I), whereas the other one is a Z′ = 1 polymorph (form II), crystallize in P21/c and P 1 space groups, respectively, and both are built by different conformers, displaying different intermolecular interactions. It is demonstrated that the usage of either CSP or NMR crystallography alone is insufficient to successfully elucidate the above-mentioned crystal structures, especially in the case of the Z′ = 2 polymorph. In addition, cases of serendipitous agreement in terms of 1H or 13C NMR data obtained for the CSP-generated crystal structures different from the ones observed in the laboratory (false-positive matches) are analyzed and described. While for the majority of analyzed crystal structures the obtained agreement with the NMR experiment is indicative of some structural features in common with the experimental structure, the mentioned serendipity observed in exceptional cases points to the necessity of caution when using an NMR crystallography approach in crystal structure determination.

scholarly journals Crystal structure prediction of organic pigments: quinacridone as an example

2007 ◽  
Vol 40 (1) ◽  
pp. 105-114 ◽  
Author(s):  
N. Panina ◽  
F. J. J. Leusen ◽  
F. F. B. J. Janssen ◽  
P. Verwer ◽  
H. Meekes ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Energy Minimization ◽  
Structure Prediction ◽  
Crystal Structure Prediction ◽  
X Ray ◽  
Organic Pigments ◽  
Structural Database ◽  
Diffraction Patterns ◽  
Experimental Structure

The structures of the α, β and γ polymorphs of quinacridone (Pigment Violet 19) were predicted usingPolymorph Predictorsoftware in combination with X-ray powder diffraction patterns of limited quality. After generation and energy minimization of the possible structures, their powder patterns were compared with the experimental ones. On this basis, candidate structures for the polymorphs were chosen from the list of all structures. Rietveld refinement was used to validate the choice of structures. The predicted structure of the γ polymorph is in accordance with the experimental structure published previously. Three possible structures for the β polymorph are proposed on the basis of X-ray powder patterns comparison. It is shown that the α structure in the Cambridge Structural Database is likely to be in error, and a new α structure is proposed. The present work demonstrates a method to obtain crystal structures of industrially important pigments when only a low-quality X-ray powder diffraction pattern is available.

scholarly journals Surface Induced Phenytoin Polymorph. 1. Full Structure Solution by Combining Grazing Incidence X-ray Diffraction and Crystal Structure Prediction

2019 ◽  
Vol 19 (11) ◽  
pp. 6058-6066 ◽  
Author(s):  
Doris E. Braun ◽  
Arianna Rivalta ◽  
Andrea Giunchi ◽  
Natalia Bedoya-Martinez ◽  
Benedikt Schrode ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Structure Prediction ◽  
Grazing Incidence ◽  
Crystal Structure Prediction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structure Solution ◽  
Full Structure

scholarly journals Crystal structure determination of an elusive methanol solvate – hydrate of catechin using crystal structure prediction and NMR crystallography

CrystEngComm ◽  
2020 ◽  
Vol 22 (30) ◽  
pp. 4969-4981 ◽  
Author(s):  
Marta K. Dudek ◽  
Piotr Paluch ◽  
Justyna Śniechowska ◽  
Karol P. Nartowski ◽  
Graeme M. Day ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Structure Determination ◽  
Structure Prediction ◽  
Crystal Structure Determination ◽  
Crystal Structure Prediction ◽  
Molecular Conformations ◽  
Nmr Crystallography

A useful short-cut was developed to limit the number of molecular conformations that need to be regarded in crystal structure prediction calculations, which led to the crystal structure determination of new methanol solvate – hydrate of catechin.

Frontiers between crystal structure prediction and determination by powder diffractometry

2008 ◽  
Vol 23 (S1) ◽  
pp. S5-S12 ◽  
Author(s):  
Armel Le Bail
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Structure Determination ◽  
Structure Prediction ◽  
Water Molecules ◽  
Crystal Structure Prediction ◽  
Large Intensity ◽  
Cell Parameters ◽  
Structure Solution ◽  
Diffraction Patterns

The fuzzy frontiers between structure determination by powder diffractometry and crystal structure prediction are discussed. The application of a search-match program combined with a database of more than 60 000 predicted powder diffraction patterns is demonstrated. Immediate structure solution (before indexing) is shown to be possible by this method if the discrepancies between the predicted crystal structure cell parameters and the actual ones are <1%. Incomplete chemistry of the hypothetical models (missing interstitial cations, water molecules, etc.) is not necessarily a barrier to a successful identification (in spite of inducing large intensity errors), provided the search-match is made with chemical restrictions on the elements present in both the virtual and experimental compounds.

Sign in / Sign up

Export Citation Format

Share Document