Details of Grant 

EPSRC Reference:	EP/R011265/1
Title:	Fundamental Studies of Electron Correlation with Applications to DFT
Principal Investigator:	Cox, Professor H
Other Investigators:
Researcher Co-Investigators:
Project Partners:
Department:	Sch of Life Sciences
Organisation:	University of Sussex
Scheme:	Standard Research
Starts:	01 May 2018	Ends:	31 January 2022	Value (£):	363,387
EPSRC Research Topic Classifications:	Physical Organic Chemistry
EPSRC Industrial Sector Classifications:	No relevance to Underpinning Sectors
Related Grants:	EP/R011656/1
Panel History:	Panel Date Panel Name Outcome 13 Sep 2017 EPSRC Physical Sciences - September 2017 Announced
Summary on Grant Application Form
Atoms, molecules and their reactions can be understood by applying quantum mechanics (QM). In order to use QM accurately in a chemical system (known as quantum chemistry), we need to understand how the electrons interact with the nuclei of the atoms in a molecule, and with each other. The problem is that the equations of QM cannot be solved exactly for systems with more than one electron, and so mainstream computational quantum chemistry is built on approximate one-electron models that treat the electron-electron interactions in an average way. However, electrons interact instantaneously and so their motion is correlated. The difference between these two approaches is known as 'electron correlation'. We cannot ignore electron correlation because the correlation energy is similar in size to the energy of making or breaking chemical bonds. Every system to which we apply quantum chemistry needs cheaper, accurate, methods for calculating this critical interaction. The first part of this proposal involves accurately calculating the electron correlation of the basic model system of two electrons and a nucleus, via an elegant series solution method. This method adds several advantages in that it is extremely computationally efficient and accurate. We will calculate highly accurate electron correlation data to develop a full understanding of how electrons interact, even at long range. The second part of this proposal involves using this new, highly accurate, correlation data to develop one of the most widely used techniques in the chemical sciences, density functional theory (DFT). DFT is currently used to provide new knowledge, and to support experimental studies, in areas ranging from nanomaterials and mineralogy to biomolecules and drug discovery. Its success derives from its unique balance of computational speed and reliability, but as DFT is stretched to more complex and exotic chemical regimes, the flaws of key underlying approximations begin to show. This puts a limit on the complexity of systems addressable by current DFT. In this work, we will design and develop two new correlation functionals for use in DFT, by fitting innovative new forms to the new highly accurate data. The first will be based on a form that accurately models electron correlation at all points from the weak to the strong electron correlation limit. The second involves an entirely new functional form. The advantage these new functionals aim to bring is increased accuracy, not only for standard applications, but also for more complex and/or exotic chemical regimes, and for systems where long-range, low-density behavior is prominent, e.g. graphene or 2-D quantum dots. Successful functionals will be implemented in the Molpro computational chemistry package so that computational scientists worldwide can gain access to high accuracy methods for use in their own cutting-edge research, enhancing the discovery of new knowledge for direct applications in the real world. The final part of this proposal involves writing new code to model excited states of three-body systems. It will include directly the electron-electron distance to model accurately the correlated motion of the electrons, and the motion of the nucleus. This will enable us to probe the electron dynamics in excited states and to calculate spectroscopic properties with nuclear motion included. Spectroscopy is an important technique in many areas of science: including atmospheric chemistry, astrochemistry, and astrophysical observations and thus can help us understand e.g. the greenhouse effect and structure of the universe. A particular emphasis will be on Rydberg atoms (large orbit atoms), as these are extremely topical in quantum computing.
Key Findings
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Organisation Website:	http://www.sussex.ac.uk