Theoretical probing of local and ultrafast phenomena using advanced light sources

In the TheoLight project, we will extend the application range of coupled cluster theory as a method to describe the ultrafast coupled motion of nuclei and electrons in chemical systems. Nuclear dynamics will be described using ab initio methods, with varying accuracy in time together with rare event path sampling techniques. We will take initial steps toward developing highly accurate electron dynamics techniques based on the time-dependent coupled cluster equations. For the local spectroscopic methods, we will use multiscale modeling to enable accurate calculations on more complex molecular systems, such as biomolecules, non-trivial surfaces, and solvated systems. In addition, spectroscopic properties for high-level methods, carefully connected to lower-level wave function theories, will be developed, and we will use a coupling to molecular mechanics and continuum models to account for environmental effects. In the project, we have developed multilevel methods and nonadiabatic coupled cluster models. We now run production calculations with the nonadiabatic code and have thus achieved the main milestones of the project.

The TheoLight project has been highly successful. The project has formed the basis for other funding applications that have been funded, this includes an Advanced ERC grant and Young Researcher grant.

In this project, we will enable and extend the applicability range of coupled cluster theory to the description of ultrafast and coupled nuclear-electron dynamics. Nuclear dynamics will be described at the ab initio level, and also a temporal multilevel aspect will be brought in by using rare event path sampling techniques. Further, we will take the intial steps in developing electron dynamics coupled cluster methods via time-dependent equations. For the local spectroscopic methods we will employ multiscale modelling to enable accurate calculations on more complex molecular systems such as biomolecules, non-trivial surfaces and solvated systems. Spectroscopic properties for high-level methods carefully connected to lower level wave function theories will be developed, and a coupling to molecular mechanics and continuum models will be employed to be able to account for environment effects.