Prof Kenneth Harris - BSc PhD CChem FRSC FRSE FLSW
- Formulation, development and application of new strategies and techniques for structure determination from powder X-ray diffraction data.
- Chemistry and physics of solid inclusion compounds, focusing on incommensurate structural properties, dynamic properties, chemical properties, crystal growth processes and the development of applications of these materials.
- Molecular motion, disorder and phase transitions in crystalline solids, with particular interest in understanding dynamics of hydrogen bonding arrangements using solid state NMR techniques.
- Fundamentals of crystallization processes and polymorphism.
The research activities of the group of Professor Harris are focused in two main directions within the general area of the Physical Chemistry of Solids.
First, we have a vigorous research programme focused on the formulation, development and application of new techniques and strategies for carrying out crystal structure determination directly from powder X-ray diffraction data, with particular emphasis on overcoming the specific challenges encountered for organic molecular materials. Our research in this area is focused on advancing fundamentals of the direct-space strategy for structure solution, which is currently based on the use of genetic algorithm search techniques. In addition to fundamental computational developments in this area, we are also applying our new techniques to tackle structural problems in a range of areas of solid state and materials sciences, including pharmaceuticals, pigments, reactive crystalline solids, electroluminescent materials, and materials of interest in structural biology.
Second, we are currently engaged in several research projects focused on understanding fundamental structural, dynamic and chemical properties of molecular solids, and the inter-relationships between these properties, particularly through studies aimed at unravelling the complex nature of solid inclusion compounds. Early research by the group in this area was focused on understanding a range of structural and dynamic aspects of one-dimensional inclusion compounds, typified by urea inclusion compounds. While continuing to advance these aspects, recent research has focused increasingly on exploiting our fundamental understanding of these materials in order to explore properties of a more applied nature, including crystal growth processes, transport processes, X-ray dichroism, and the development of strategies for direct experimental determination of intermolecular interaction energies. Other topics of active interest include dynamics of hydrogen bonding arrangements in solids, molecular quasicrystals, and fundamentals of polymorphism and crystallization processes in organic solids.
A new in situ solid-state NMR technique has been developed to map the evolution of different polymorphic forms of a solid during crystallization from solution. The first results obtained, for the crystallization of glycine from D2O, reveal that nucleation yields the α polymorph, which then undergoes a solution-mediated transformation to produce the γ polymorph.
Techniques that we are developing for carrying out structure determination directly from powder X-ray diffraction data have been exploited to understand structural properties of the solid-state photopolymerization reaction of 2,5-distyrylpyrazine. The structure of the polymeric product (orange) in this case was determined from powder X-ray diffraction. The structural relationship between the reactant (green) and product (orange) phases confirms the topochemical nature of this solid-state transformation.