EPSRC Reference: 
EP/C520548/1 
Title: 
Accurate Equilibrium Structures from Experimental Data 
Principal Investigator: 
Rankin, Professor D 
Other Investigators: 

Researcher CoInvestigators: 

Project Partners: 

Department: 
Sch of Chemistry 
Organisation: 
University of Edinburgh 
Scheme: 
Standard Research (PreFEC) 
Starts: 
01 September 2005 
Ends: 
31 August 2008 
Value (£): 
177,869

EPSRC Research Topic Classifications: 

EPSRC Industrial Sector Classifications: 
No relevance to Underpinning Sectors 


Related Grants: 

Panel History: 

Summary on Grant Application Form 
The structures of molecules  their shapes and sizes  are fundamentally important to understanding properties of molecules. They can be determined by experiments (usually electron diffraction for gaseous molecules), or by using purely theoretical methods and powerful computers. Both methods give good, but not perfect, results  but, unfortunately, they don't measure the same thing. Because of effects arising from movements of atoms, experimental distances are slightly different from those that are calculated. Neither is wrong; they are just defined differently. This makes it very difficult to compare experimental and computed structures and, in particular, to see whether new computational methods are getting things right.This research sets out to bridge the gap, by calculating the differences between the two types of distance. We will do this by following the motion of the atoms as they vibrate, and seeing how their average positions differ from those in their socalled 'equilibrium' positions. By applying these calculated differences to experimental distances, we will be able to determine equilibrium structures  the same as those obtained by theoreticians.The same methodology can also be applied to make experimental structures more accurate. At present, interpretation of diffraction data for gases, which gives the structures, uses equations that work by considering every possible pair of atoms in a molecule. This ignores contributions from all the possible sets of three atoms, which can be very significant. However, this contribution is usually ignored, because the theory is not sufficiently developed. We will work out how to calculate these terms, and to make inclusion of them a routine matter.The result? More accurate structures, and more meaningful, as they will relate to computed structures.

Key Findings 
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Potential use in nonacademic contexts 
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Impacts 
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Summary 

Date Materialised 


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Organisation Website: 
http://www.ed.ac.uk 