Vibrational Circular Dichroism and Electronic Currents from First Principles

• Applicant: Dr. Sascha Jähnigen
• Subject Area: Theoretical Chemistry: Electronic Structure, Dynamics, Simulation
• Term: from 2021 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 451539523

Vibrational circular dichroism (VCD) is an uprising spectroscopic technique with an increasing scope of applicability in both, academia and industry. Referring to the absorption difference of left- and right-circularly polarised light, VCD can be considered as “chiral IR spectroscopy”. It has become an invaluable tool in the determination of absolute configurations by assigning recorded spectra to structural information obtained from theoretical calculations. Yet, VCD is highly sensitive towards supramolecular effects around the chiral centre, be it the dependence of a solution spectrum on the solvent or the influence of chiral crystal packing in solid-state. A crucial point lies in the availability of efficient theoretical models that are to be referred to when interpreting experimental results. Many applications of VCD do not materialize due to the lack of suitable theoretical models. The recent years saw the wealth of theoretical methods growing steadily – fueled by continuous augmentation of affordable computational power. Innovative approaches allow for realistic simulations that can be considered as "virtual experiments". This project aims to push forward landmark innovations of computational chemistry by combining ab initio molecular dynamics (AIMD) and the formalism of Nuclear Velocity Perturbation Theory (NVPT). The theoretical framework of NVPT has only recently been implemented into the CPMD code and awaits numerous applications. AIMD+NVPT are an attractive means to compute VCD spectra based on an accurate sampling of anharmonic free energies; the preceding work has already underlined the impact if this method. This success will be followed up by this project. Yet, there are many more applications in spectroscopy, but also organic chemistry and more fundamental in quantum chemistry that form the important second pillar of the proposed research. The latter also aims for diversifying the profile of the researcher, benefiting from the host researcher's network and expertise in a world-leading institution in quantum physics and chemical computation. To communicate the theoretical results in a highly illustrative fashion to a broad audience, this project explicitly puts effort into devising instructive and educational means of visualization and to improve the techniques' ease of use through a comprehensive python package.

• DFG Programme: WBP Fellowship
• International Connection: France
• Host: Professor Dr. Rodolphe Vuilleumier