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Electron Correlation - The Electronic Ground State of Graphene Nanoribbons

Final Report Summary - ELECTRON CORRELATION (Electron Correlation - The Electronic Ground State of Graphene Nanoribbons)

The main goal of the project “Electron Correlation” is to develop an accurate and efficient method to describe electron correlation in molecules. In particular the static correlation is focused on as it has been notoriously difficult to treat. Static correlation is predominant in the bond dissociation region of molecules. As a consequence it is expected that the project will enhance the description of bond cleavage and bond forming processes, the most important processes in Chemistry.

Two methods were identified to serve as the basis for the development. Density Functional Theory (DFT) on the one hand and Density Matrix Functional Theory (DMFT) on the other hand were to be combined. To this end the research would center around short range DFT + long range DMFT (srDFT+lrDMFT) developed by the fellow in collaboration with Prof. Katarzyna Pernal.

Building upon a recent collaboration the first focus was on the development of a new DFT method. The random phase approximation (RPA) has recently been implemented self-consistently by the fellow. The implementation was extended to allow for spin-polarized or unrestricted calculations.

Calculations on a small test system revealed important new insights. The dissociation curve of the H2 molecule does not exhibit the highly discussed “bump” at intermediate distances. In contrast, the energy saturates at physical bond distances. In addition, now fractional spin error is observed at the dissociation limit.