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Development of multi-level electron correlation methods in quantum chemistry

Final Report Summary - NEWQUANTUM (Development of multi-level electron correlation methods in quantum chemistry)

The project NEWQUANTUM has in all aspects been highly successful. The project has made a reorientation of my research possible and this in turn has lead to high productivity and innovative research. The training I have received during my collaborations with experimentalists and theoreticians will be invaluable to my future academic career. The support provide by Stanford University, NTNU and The Norwegian Research Council has been second to none.

In the beginning of the project I set out to improve the application range of quantum chemistry methods using multi-level techniques. During the last three years, I have together with my collaborators succeeded in developing several new approaches and they appear very promising. These developments have focused on Hartree-Fock and coupled cluster theories, with emphasis on response properties.

Shortly after arriving at Stanford University, the first period of the project, I got involved in a collaboration with the experimental group lead by Prof. Markus Gühr, on the excited state dynamics of thymine. This collaboration has spurred many development project in coupled cluster theory for X-ray phenomena. The results of the collaboration has been published in Nature Communications and SLAC published in this connection the following press release: https://www6.slac.stanford.edu/news/2017-06-22-single-electrons-tiny-leap-sets-molecular-sunscreen-response.aspx

During the thymine collaboration, we encountered some very fascinating conical intersections. A notorious case in coupled cluster theory is the inability to describe these phenomena. During the second period of the project at NTNU, we have made a concerted effort to resolve this long-standing problem. I'm please that we now have resolved the problem and can submit our findings for publication.