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TYC Lunchtime Get-Together - January 2018

Dr David Case, Luca Luzzolino,

Alex Aina, Dr Rui Guo

Friday 19 October 2017
Time: 1-2pm
Venue: Physics Building, Room E7, UCL
Contact: Karen Stoneham
Tel: 0207 6797306

Control and Prediction of the Organic Solid State

This talk will be comprised of four parts, with each presented by a different speaker; all will describe aspects of work in the group of Sally Price, to apply and develop methods of modelling the organic solid state. The particular focus is on crystal structure prediction (CSP), the goal of which is to predict the structure of a macroscopic organic crystal from the molecular structure of its components. The first part of this seminar (Dave Case) will be to introduce the different methodologies, the challenges and the potential of the field, whilst contrasting the differences between approaches required to model the organic solid state to those applicable to other types of materials.

One of the main limitations of CSP studies is the large computational cost that they require, particularly for conformationally flexible pharmaceutical molecules, which tend to have several bulky fragments linked by flexible torsion angles. In the second talk, Luca Iuzzolino will outline how an effective workflow can be developed, which significantly speeds up CSP studies without any significant decrease in the overall quality of the results. Approaches based on the use of databases during the generation of candidate crystal structures, and the use of density functional tight-binding (DFTB) during their optimisation and ranking with respect to lattice energy will be discussed. Each step of the methodology is compared to test data on a set of five pharmaceutical-like molecules, where an extensive CSP study had already been performed.

The third section (Alex Aina) will discuss the theory of intermolecular forces and the development and testing of non-empirical force-fields for weakly-bound organic molecular crystals. The advantages of developing realistic models using state-of-the-art theory, as opposed to empirical fitting, which absorbs thermal effects and other approximations, are shown for cases wherein the accurate prediction of properties that sample high temperatures and pressures are required.

Understanding the relative stability of organic polymorphs requires a knowledge of their phonon structures. However this remains a challenging task even with the rapid progress of available periodic DFT codes, due to much weaker intermolecular interactions and the fact that most of these codes were initially developed with inorganic or metallic materials in mind. The final talk (Rui Guo) will detail our recent efforts to tackle these problems, and move our calculations beyond the zero Kelvin limit.

  • Sally Price group Jan 2018.jpg
    Sally Price group
    Control and Prediction of the Organic Solid State
Sally Price group Jan 2018.jpg
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