Electronic Structure Modeling With the Strictly Correlated Electrons Density Functional

• Applicant: Andre Mirtschink, Ph.D.
• Subject Area: Theoretical Chemistry: Electronic Structure, Dynamics, Simulation ; Theoretical Chemistry: Molecules, Materials, Surfaces
• Term: from 2015 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 286260895

Density functional theory (DFT) is routinely applied for electronic structure calculations in biology, chemistry and physics. To guarantee computational efficiency one employs the Kohn-Sham (KS) reference system of non-interacting electrons and functional approximations are used to model the physical interaction. Challenges arise when strong electronic correlation is targeted within the non-interacting framework with traditional approximations being deficient in this regard. As recent breakthrough in the development of functional approximations the strictly correlated electrons (SCE) functional was introduced in KS-DFT. It derives rigorously from the strong-interaction limit of DFT and in the course of my PhD research I did demonstrate that it can capture strong-correlation effects from first principles.Moreover I did demonstrate a derivative discontinuity in the SCE functional. This formal feature is often crucial for the computation of electron dynamics but is missed in traditional approximations . Hence, improvements are expected in the DFT modeling of dynamical processes and in this project I will investigate the SCE functional in this context. One dimensional model setups will be used to analyze the capabilities of the SCE functional from formal grounds. Special interest will be devoted to phenomena that require a derivative discontinuity in the functional approximation for a proper modeling.Due to the striking formal properties of the SCE functional improvements are expected in the DFT modeling beyond strongly correlated systems. Prior to a general application of the SCE functional, however, strategies are required for its solution in three dimensions. To devise a SCE solution in three dimensions I will analyze in the following the building blocks of the SCE functional, the so-called co-motion functions, for the Hydrogen molecule where accurate reference data is available. If no exact formulas for the reconstruction of the co-motion functions can be found approximate strategies will be pursued. Finally extensions will be attempted to solve the SCE functional for diatomic molecules with many electrons. To guarantee for a good accuracy of the method in all correlation regimes quantitative corrections to the KS-SCE functional can be considered and improved.With the developments of this project non-empirical parameters can be provided for multi-scale modeling methods like the density-functional tight-binding method (DFTB). Although adaptions of the DFTB method are required for a proper incorporation of the SCE parameters, the developments can lead to a reliable method for the modeling of very large molecular systems or complex solids.

• DFG Programme: Research Fellowships
• International Connection: Spain
• Host: Professor Dr. Angel Rubio