Details of Grant 

EPSRC Reference:	EP/F010974/1
Title:	Expanding the scope and scale of first-principles quantum-mechanical simulations with the ONETEP linear-scaling method on high performance computers
Principal Investigator:	Haynes, Professor PD
Other Investigators:
Researcher Co-Investigators:
Project Partners:
Department:	Physics
Organisation:	Imperial College London
Scheme:	Standard Research
Starts:	01 October 2007	Ends:	31 March 2009	Value (£):	135,970
EPSRC Research Topic Classifications:	Condensed Matter Physics High Performance Computing
EPSRC Industrial Sector Classifications:	Information Technologies
Related Grants:
Panel History:	Panel Date Panel Name Outcome 16 Apr 2007 HPC Software Development (Science) Announced
Summary on Grant Application Form
Computer simulations play an important part in our society e.g. flight simulators allow pilots to be trained more cheaply and safely than in the air. In science and technology, computer simulation is a powerful tool for understanding and predicting complex processes in materials. Simulations are often used alongside conventional experiments, but they can also be used when experiments are too expensive or even impossible to perform, e.g. when studying materials in extreme conditions such as the high temperatures and pressures at the centre of the Earth.The turn of the last century saw the start of a scientific revolution with the discovery of quantum mechanics (QM). On very small scales, nature behaves in a radically different way from our everyday experience. If we were shrunk down to the size of an atom navigation would become very difficult, as the uncertainty principle says that it is impossible to know at the same moment precisely where you are and where you are going! In spite of this bizarre behaviour, QM is astonishingly accurate, and provides the foundation for all our science and technology.Such claims are of no use unless the equations of QM can be solved for problems of interest to scientists and engineers today. The challenge is that the equations are very complicated - even two electrons are too much for finding a solution on paper. In a way, QM has itself provided the answer as it led to the invention of the transistor and so to the computer. However, even on the fastest computers it is only possible to solve the equations of QM exactly for small molecules, whereas the systems of interest to scientists today involve many thousands. Even the rapid and relentless progress of computer technology cannot provide the whole answer, because of the scaling of the problem.The work needed to accomplish a certain task generally increases with its size e.g. the time taken to mow a lawn is proportional to its area: if you double the size of your garden it will take you twice as long. This is an example of linear scaling, but the effort involved in many tasks increases faster than this. Sorting a set of books or CDs into alphabetical order or arranging your hand in a game of cards usually scales as the square of the number of objects involved: if you triple the number it will take nine (three squared) times as long. There are some tasks which are much worse, such as solving the travelling salesman problem to find the quickest route to visit a given set of places. Adding one more location doubles the time it takes to solve. Even if you can solve the problem for three locations in one minute, just 22 will take you a whole year. Solving the equations of QM exactly scales like this. However, in the 1960s a significant leap forwards was made with the introduction of density-functional theory (DFT), for which Walter Kohn won the 1998 Nobel Prize in chemistry. The origin of the unfavourable scaling is that electrons are charged particles. Like charges repel, so one electron's trajectory depends on all the others', as it wants to avoid them. So solving the equations which describe these trajectories becomes much harder as more electrons are involved. But the remarkable result of DFT is that the physical properties of the whole system, the answers to the questions we want, do not depend upon the details of these individual trajectories, but only on the average. So a linear-scaling solution of the equations is possible, which promises dramatically to expand the scale of quantum simulations accessible.The aim of this work is to adapt a recently-developed linear-scaling DFT code called ONETEP to take advantage of recent developments in computer technology so that it runs efficiently on the most powerful computers now available. Harnessing the power of linear-scaling methods and modern computers will allow scientists to perform simulations based on QM for systems made of tens of thousands of atoms for the first time.
Key Findings
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Project URL:	http://www.onetep.org/
Further Information:
Organisation Website:	http://www.imperial.ac.uk