Department of Chemistry

Structure prediction and lattice dynamics in molecular crystals

The main focus of our research is on the development and application of computational methods for understanding the structure and properties of molecular crystals, with the aim of guiding experiments towards the design and discovery of novel molecular materials.

Crystal structure prediction: The goal of crystal structure prediction is to be able to predict, from first principles, how a given molecule will arrange itself in a crystal; it is the packing of molecules and the various intermolecular interactions that determine many of a crystal's physical properties, such as colour, stability and compressibility. Therefore, reliable predictive computational methods could be an important tool for the rational design of materials. In our development of methods for crystal structure prediction, we are exploring the balance of many factors - packing energy vs. entropy, conformational energy vs. intermolecular interactions and thermodynamics vs. kinetics - that determine a crystal's structure.

Lattice dynamics and terahertz spectroscopy: As well as predicting how a molecule will crystallise, we are interested in improving our understanding of the lattice dynamics in molecular crystals: the whole-molecule vibrations about their equilibrium positions. One motivation for modelling the dynamics in crystals is to improve our understanding of the relative stabilities and physical properties of crystal forms. Our dynamics simulations are also aimed at characterising features observed in terahertz spectra of molecular crystals (0.1 - 6 THz = 3 - 200 cm^-1). Terahertz spectroscopy is a promising tool for the monitoring of polymorphism of organic molecules because it is a direct probe of the intermolecular forces between molecules.

Selected Publications

Prediction and observation of isostructurality induced by solvent incorporation in multicomponent crystals, Journal of the American Chemical Society, 128, 14466 (2006)

A strategy for predicting the crystal structures of flexible molecules: the polymorphism of phenobarbital, Physical Chemistry Chemical Physics, 9, 1693 (2007)

Terahertz time-domain spectroscopy and the quantitative monitoring of mechanochemical cocrystal formation, Nature Materials, 6, 206 (2007)

Understanding the influence of polymorphism on phonon spectra: lattice dynamics calculations and terahertz spectroscopy of carbamazepine, Journal of Physical Chemistry B, 110, 447 (2006)

Modeling the interplay of inter- and intra-molecular hydrogen bonding in conformational polymorphs, The Journal of Chemical Physics, 128, 244708, (2008)