28 research outputs found

    Report on the sixth blind test of organic crystal-structure prediction methods

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    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 submissions, 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

    Towards crystal structure prediction of complex organic compounds - a report on the fifth blind test

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    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

    Subtask 4.6: Kerogen/asphaltene/mineral matrix: Structure and interactions

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    presentationA presentation given at the Unconventional Fuels from Oil Shale and Oil Sands Project Review Meeting on March 10-11, 2011

    Structural characterization of Green River oil shale core segments and the kerogen isolated from these segments

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    presentationThe goal is to obtain information about chemical structure of oil shale and its kerogen. This includes chemical characterization of the shale, the isolated kerogen, and the products of pyrolysis of both the shale and kerogen, and provides data for validation of modeling component of the project (later talk in this session)

    Carbon-13 Chemical Shift Tensors in Pentaerythritol

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    NMR at Cryogenic Temperatures:  A 13

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    Cluster Analysis of 13

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