Simulating moleCulaR nonlinEar spEctrosCopies for Heavy elemEntS – SCREECHES

The understanding of interaction between matter and light is one of the keys to unlock our understanding of natural phenomena, be it from a fundamental or application-oriented research standpoints, since light-matter interaction is central to many technologies and processes that are central to our societies : for example in medical science (imaging), energy generation (photovoltaic devices) or telecommunications (photonics devices, consumer electronics). The main objective is to develop novel theoretical tools to accurately simulate multi-photon processes for molecular systems that are applicable across the periodic table, for gas-phase and solvated or otherwise confined systems by taking into account relativistic, electron correlation and environment effects; and for resonant and off-resonant processes, and capable to handle any combination of electric and magnetic perturbations, allowing for the investigation of optical properties related to chirality. Beyond these developments, we aim to carry out first applications of these methods to investigate systems containing heavy elements (focusing here on lead perovskites and actinide molecules), due to their importance in many technological applications and the challenges faced by theoretical approaches in accurately describing them. The project’s main activities will involve devising and implementing high-order response theory based on the relativistic coupled cluster singles and doubles model, addressing resonant processes involving both valence and core electrons. The implementation will be carried out within the scalable ExaCorr module of the DIRAC program package, in order to enable accurate calculations for systems containing up to around 50 atoms and including one or more heavy elements. To expand the utility of these methods, we will also incorporate quantum embedding techniques.