Details of Grant 

EPSRC Reference:	EP/C539109/1
Title:	Development of accurate intermolecular potentials for organic molecules, and their application to the solid state
Principal Investigator:	Price, Professor SL
Other Investigators:	Leslie, Dr M
Researcher Co-Investigators:	Dr AJ Misquitta Professor AJ Stone
Project Partners:	University of Delaware
Department:	Chemistry
Organisation:	UCL
Scheme:	Standard Research (Pre-FEC)
Starts:	01 June 2005	Ends:	31 December 2008	Value (£):	272,598
EPSRC Research Topic Classifications:	Chemical Structure Physical Organic Chemistry
EPSRC Industrial Sector Classifications:	No relevance to Underpinning Sectors
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Summary on Grant Application Form
The forces between molecules control most of their properties in the gas, liquid and various solid forms, and also how they interact with other molecules within living organisms. However, obtaining an equation that quantifies the intermolecular forces sufficiently accurately that we can compute the physical properties of the solids, liquids, gases, and clusters of molecules in agreement with experiment has only been possible for the noble gases, and more recently, small molecules such as water. A major reason for this has been the subtlety with which important intermolecular interactions depend on the behaviour of the electrons within the molecule. We need to perform very expensive quantum mechanical calculations that describe the fluctuations in the electron density within the molecules that cause the molecules to attract each other.In this proposal, we will develop the Latest theoretically based quantum rnechanical methods designed for intermolecular forces and the theory to produce quantitative atom-atom models for the interactions between organic molecules. These mathematical models have a significantly more complex functional form than those currently used in computer modelling of the behaviour of organic and biological molecules, for example, showing how the neighbouring molecules distort each others electron distribution. By using such accurate models for the intermolecular forces, we will be able to quantitatively understand and predict the behaviour of molecules and also help develop better theories for calculating their properties. We will pioneer the use of these theoretically well-based models in computational prediction of the behaviour of molecules, by developing the most advanced programs for modelling clusters and crystals. In particular we will apply the new models for their intermolecular forces to understand why pyridine, tetrolic and oxalic acids can each crystallise in two different solid structures, by performing calculations on the known crystal structures and a range o' hypothetical ones. Our resulting understanding how the subtleties of the intermolecular forces lead to multiple crystal structures will benefit the pharmaceutical, pigments and other molecular materials industries, where the occurrence of multiple crystal forms with different physical properties is a major problem in quality control.Thus this research will produce a theoretically based method of modelling the forces between molecules that should move the computer modelling of organic interactions from using models that are derived from experiment using poorly justified assumptions, to models that are based on the molecules' quantum mechanical behaviour and are therefore more realistic and reliable.
Key Findings
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Potential use in non-academic contexts
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Project URL:	http://www-stone.ch.cam.ac.uk/programs.html
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