Research Interests

Intermolecular forces: The development and application of realistic model potentials

The electrostatic potential around cytosine, derived using Distributed Multipole Analysis 

Intermolecular forces determine the structure and physical properties of molecular solids and liquids, and play a major role in many biochemical processes, such as drug-receptor binding. Our research involves exploiting recent advances in the theory of intermolecular forces to derive highly accurate model intermolecular potentials from the ab initio electron distributions of the molecules. The novel feature of these model potentials is that they represent non-spherical features in the charge distribution, such as lone pair and [pi] electron density, and thus can represent hydrogen bonding. Thus, these anisotropic atom-atom potentials are far more realistic, and mathematically sophisticated, than the isotropic atom-atom potentials which are generally used in simulations. We are using these state-of-the-art model potentials to study a wide range of problems, with particular emphasis on the organic solid state.

The anisotropic atom-atom potential have proved very sucessful in reproducing the crystal structures of a wide range of polar and hydrogenic molecules, from nucleic acid bases, pharmaceuticals, energetic and non-linear optical materials. We are now using these potentials and a systematic search through common packing motifs to find the minima in the lattice energy, and thus predict the crystal structures of various organic molecules. In cases where there are more energetically feasible crystal structures than known polymorphic forms, we wish to model the other factors which determine which crystal structures will be found. We are therefore studying crystal growth and morphology and elastic properties of organic crystals, and developing Molecular Dynamics to investigate effects of temperature on crystal stabiloty.

The unit cell of alloxan (from the Cambridge Structural Database)