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1.  Report on the sixth blind test of organic crystal structure prediction methods 
Reilly, Anthony M. | Cooper, Richard I. | Adjiman, Claire S. | Bhattacharya, Saswata | Boese, A. Daniel | Brandenburg, Jan Gerit | Bygrave, Peter J. | Bylsma, Rita | Campbell, Josh E. | Car, Roberto | Case, David H. | Chadha, Renu | Cole, Jason C. | Cosburn, Katherine | Cuppen, Herma M. | Curtis, Farren | Day, Graeme M. | DiStasio Jr, Robert A. | Dzyabchenko, Alexander | van Eijck, Bouke P. | Elking, Dennis M. | van den Ende, Joost A. | Facelli, Julio C. | Ferraro, Marta B. | Fusti-Molnar, Laszlo | Gatsiou, Christina-Anna | Gee, Thomas S. | de Gelder, René | Ghiringhelli, Luca M. | Goto, Hitoshi | Grimme, Stefan | Guo, Rui | Hofmann, Detlef W. M. | Hoja, Johannes | Hylton, Rebecca K. | Iuzzolino, Luca | Jankiewicz, Wojciech | de Jong, Daniël T. | Kendrick, John | de Klerk, Niek J. J. | Ko, Hsin-Yu | Kuleshova, Liudmila N. | Li, Xiayue | Lohani, Sanjaya | Leusen, Frank J. J. | Lund, Albert M. | Lv, Jian | Ma, Yanming | Marom, Noa | Masunov, Artëm E. | McCabe, Patrick | McMahon, David P. | Meekes, Hugo | Metz, Michael P. | Misquitta, Alston J. | Mohamed, Sharmarke | Monserrat, Bartomeu | Needs, Richard J. | Neumann, Marcus A. | Nyman, Jonas | Obata, Shigeaki | Oberhofer, Harald | Oganov, Artem R. | Orendt, Anita M. | Pagola, Gabriel I. | Pantelides, Constantinos C. | Pickard, Chris J. | Podeszwa, Rafal | Price, Louise S. | Price, Sarah L. | Pulido, Angeles | Read, Murray G. | Reuter, Karsten | Schneider, Elia | Schober, Christoph | Shields, Gregory P. | Singh, Pawanpreet | Sugden, Isaac J. | Szalewicz, Krzysztof | Taylor, Christopher R. | Tkatchenko, Alexandre | Tuckerman, Mark E. | Vacarro, Francesca | Vasileiadis, Manolis | Vazquez-Mayagoitia, Alvaro | Vogt, Leslie | Wang, Yanchao | Watson, Rona E. | de Wijs, Gilles A. | Yang, Jack | Zhu, Qiang | Groom, Colin R.
The results of the sixth blind test of organic crystal structure prediction methods are presented and discussed, highlighting progress for salts, hydrates and bulky flexible molecules, as well as on-going challenges.
The sixth blind test of organic crystal structure prediction (CSP) methods has been held, with five target systems: a small nearly rigid molecule, a polymorphic former drug candidate, a chloride salt hydrate, a co-crystal and a bulky flexible molecule. This blind test has seen substantial growth in the number of participants, with the broad range of prediction methods giving a unique insight into the state of the art in the field. Significant progress has been seen in treating flexible molecules, usage of hierarchical approaches to ranking structures, the application of density-functional approximations, and the establishment of new workflows and ‘best practices’ for performing CSP calculations. All of the targets, apart from a single potentially disordered Z′ = 2 polymorph of the drug candidate, were predicted by at least one submission. Despite many remaining challenges, it is clear that CSP methods are becoming more applicable to a wider range of real systems, including salts, hydrates and larger flexible molecules. The results also highlight the potential for CSP calculations to complement and augment experimental studies of organic solid forms.
doi:10.1107/S2052520616007447
PMCID: PMC4971545  PMID: 27484368
crystal structure prediction; polymorphism; lattice energies; Cambridge Structural Database
2.  Accurate and efficient representation of intra­molecular energy in ab initio generation of crystal structures. I. Adaptive local approximate models 
This article describes an important improvement in the CrystalPredictor II code: adaptive Local Approximate Models (LAMs). This improvement allows the most efficient use of computational effort to cover a flexible molecule’s conformational space, and is illustrated with a crystal structure prediction (CSP) investigation into the sixth blind test molecule 26.
The global search stage of crystal structure prediction (CSP) methods requires a fine balance between accuracy and computational cost, particularly for the study of large flexible molecules. A major improvement in the accuracy and cost of the intramolecular energy function used in the CrystalPredictor II [Habgood et al. (2015 ▸). J. Chem. Theory Comput. 11, 1957–1969] program is presented, where the most efficient use of computational effort is ensured via the use of adaptive local approximate model (LAM) placement. The entire search space of the relevant molecule’s conformations is initially evaluated using a coarse, low accuracy grid. Additional LAM points are then placed at appropriate points determined via an automated process, aiming to minimize the computational effort expended in high-energy regions whilst maximizing the accuracy in low-energy regions. As the size, complexity and flexibility of molecules increase, the reduction in computational cost becomes marked. This improvement is illustrated with energy calculations for benzoic acid and the ROY molecule, and a CSP study of molecule (XXVI) from the sixth blind test [Reilly et al. (2016 ▸). Acta Cryst. B72, 439–459], which is challenging due to its size and flexibility. Its known experimental form is successfully predicted as the global minimum. The computational cost of the study is tractable without the need to make unphysical simplifying assumptions.
doi:10.1107/S2052520616015122
PMCID: PMC5134761  PMID: 27910837
crystal structure prediction; solid-state science; local apprioximate model
3.  Towards crystal structure prediction of complex organic compounds – a report on the fifth blind test 
Following on from the success of the previous crystal structure prediction blind tests (CSP1999, CSP2001, CSP2004 and CSP2007), a fifth such collaborative project (CSP2010) was organized at the Cambridge Crystallographic Data Centre. A range of methodologies was used by the participating groups in order to evaluate the ability of the current computational methods to predict the crystal structures of the six organic molecules chosen as targets for this blind test. The first four targets, two rigid molecules, one semi-flexible molecule and a 1:1 salt, matched the criteria for the targets from CSP2007, while the last two targets belonged to two new challenging categories – a larger, much more flexible molecule and a hydrate with more than one polymorph. Each group submitted three predictions for each target it attempted. There was at least one successful prediction for each target, and two groups were able to successfully predict the structure of the large flexible molecule as their first place submission. The results show that while not as many groups successfully predicted the structures of the three smallest molecules as in CSP2007, there is now evidence that methodologies such as dispersion-corrected density functional theory (DFT-D) are able to reliably do so. The results also highlight the many challenges posed by more complex systems and show that there are still issues to be overcome.
doi:10.1107/S0108768111042868
PMCID: PMC3222142  PMID: 22101543
4.  Towards crystal structure prediction of complex organic compounds – a report on the fifth blind test 
The results of the fifth blind test of crystal structure prediction, which show important success with more challenging large and flexible molecules, are presented and discussed.
Following on from the success of the previous crystal structure prediction blind tests (CSP1999, CSP2001, CSP2004 and CSP2007), a fifth such collaborative project (CSP2010) was organized at the Cambridge Crystallographic Data Centre. A range of methodologies was used by the participating groups in order to evaluate the ability of the current computational methods to predict the crystal structures of the six organic molecules chosen as targets for this blind test. The first four targets, two rigid molecules, one semi-flexible molecule and a 1:1 salt, matched the criteria for the targets from CSP2007, while the last two targets belonged to two new challenging categories – a larger, much more flexible molecule and a hydrate with more than one polymorph. Each group submitted three predictions for each target it attempted. There was at least one successful prediction for each target, and two groups were able to successfully predict the structure of the large flexible molecule as their first place submission. The results show that while not as many groups successfully predicted the structures of the three smallest molecules as in CSP2007, there is now evidence that methodologies such as dispersion-corrected density functional theory (DFT-D) are able to reliably do so. The results also highlight the many challenges posed by more complex systems and show that there are still issues to be overcome.
doi:10.1107/S0108768111042868
PMCID: PMC3222142  PMID: 22101543
prediction; blind test; polymorph; crystal structure prediction

Results 1-4 (4)