Light–Matter Interactions in Complex Molecular Systems

SNIC 2022/1-19


SNIC Large Compute

Principal Investigator:

Patrick Norman


Kungliga Tekniska högskolan

Start Date:


End Date:


Primary Classification:

10407: Theoretical Chemistry



This project is concerned with the calculation of spectroscopic properties of complex molecular systems, driven by collaborations with experimental partners. We have been awarded a KAW project to develop theory and conduct simulations of contemporary and future X-ray spectroscopies at MAX IV and free-electron laser (XFEL) facilities around the world. We are uniquely able to conduct simulations of the full Kramers-Heisenberg-Dirac electronic response function describing the resonant inelastic X-ray scattering (RIXS) process for which a dedicated beamline VERITAS is constructed at MAX IV as well as X-ray multi-photon processes relevant for experiments using XFELs. We will for instance in this project unravel molecular synthetic design strategies to optimise X-ray nonlinear responses. This corresponds to the vast amount of work invested in optimising molecular materials for two-photon absorption in the UV/vis spectral region and which has lead to an understanding that conjugated systems with charge donating and accepting moieties serve as excellent candidates. In the X-ray spectral region there is presently no experience of this kind and we will establish such with studies of a selection of molecular classes as to guide future experiments performed in collaboration with us (key collaborator: Prof. A. Nilsson, Stockholm University). We have been awarded two grants from the European Commission that as a component involve the simulation of interactions between molecular luminescence probes and amyloid proteins acting as precursors and hallmarks of protein misfolding diseases such as Alzheimer's and Parkinson's. Our aim in this research is to obtain a microscopic understanding of the docking between probe and amyloid as well as its consequences on the molecular dynamics that in turn give rise to signature fingerprints in emission spectra. This work is performed in close collaboration with experimental activities (key collaborator: Prof. P. Nilsson, Linköping University). We have been awarded one grant from the American Air Force Research Laboratory (AFRL) via its European office (EOARD) to develop the next generation of molecular glass materials for optical power limiting (OPL) applications. Quantum chemical simulations show that enhanced protection against laser damage can be achieved at a constant chromophore concentration by means of alignment of the optical axes of molecules during the glass preparation. Further work based on molecular dynamics simulations will reveal the conditions under which such an orientation can be achieved under realistic conditions using static electric fields. An experimental station will be built at FOI in Linköping for this purpose (key collaborator is Dr C. Lopes). Other projects based on more general funding from the faculty and the Swedish Research Council (VR) include our strive to study the tertiary structure of DNA and the regulatory mechanisms in chromatin function by means of electronic circular dichroism (CD) spectroscopy. We have built a methodology for calculating the CD responses of DNA sequences by means of first principles methods and we have been able to show how the tertiary structure affects the signal strength.