CSP Blind Test

Following on from the fantastic advances made through the past CSP blind tests, the seventh test posed new challenges, asks deeper questions, and examines method developments closely.

A summarised form of the rules and entry pack is provided.

How to participate once you have registered for the CSP Blind Test.

The fifth blind test ran in 2010 with the final summary report published in 2011. The test included a variety of targets, from rigid and semi-flexible molecules, to a 1:1 salt, as well as a larger more flexible molecule and a hydrate with multiple polymorphs. While there were fewer successful results than previous years, there was at least one successful result for each target. The results also showed the progress made in methodologies such as dispersion-corrected density functional theory (DFT-D) which has become much more reliable.

Target XX in the fifth CSP Blind Test – a highly flexible compound with eight exocyclic torsion angles. Benzyl-(4-(4-methyl-5-(p-tolylsulfonyl)-1,3-thiazol-2-yl)phenyl)carbamate (C₂₅H₂₂N₂O₄S₂)

The fourth blind test started in 2007, with 14 research groups taking part. Across the four targets, we saw a dramatic improvement in successful predictions compared to previous tests. This reflects important improvements in methods and suggest that for small and rigid molecules calculations are able to aid understanding in crystallization and polymorphism of organic molecules.

Molecule XIV from the fourth CSP Blind Test – N-(Dimethylthiocarbamoyl)benzo­thiazole-2-thione (C₁₀N₁₀N₂S₃)

In the third CSP blind test a range of methods were employed by the 18 participating research groups. Most were based on the global minimization of lattice energy. Three targets were provided, with no restriction on the possible space group – unlike previous tests.

The test saw lower success rates than previous ones, in part due to complexities in some of the targets. This highlights the need for better energy models which can describe conformational and packing energies with high accuracy.

Molecule XI from the third CSP Blind Test – Azetidine. With several possible arrangements for hydrogen bonding, the crystal structure is built up from chains containing two azetidine molecules in the asymmetric unit.

The second CSP Blind Test saw 17 participants predict the crystal structure of three organic molecules. A maximum of three predictions were allowed for each molecule, with many correct predictions observed. A secondary test using non-indexed powder diffraction data was performed after submissions.

A collaborative workshop was held to test how well current methods of crystal structure prediction perform. The 11 participants were presented with the molecular structure of four compounds, which had been experimentally determined but as-yet unpublished. None of the methods gave consistently reliable results, but many proposed structures were close to the experimentally observed one. One target compound was observed to have two polymorphs, but only one form was predicted correctly.