Light-matter Interaction: Multiscale, Multicalculator Modelling with Atomic Simulation Environment

The description of light-matter interactions is becoming a vital part of computational chemistry, not only as non-coherent environment-system background interactions such as thermal baths, absorption and emission, but with light having active role such as cavity quantum electrodynamics, strong coupling, photonic crystals, polaritonic chemistry and Bose-Einstein polaritonic lasing, to name a few. Simulating light-matter systems requires multiscale modelling due to vast scale differences. I will present my current work on solving Maxwell–Kohn–Sham equations, with multiple Time-Dependent Density Functional Theory systems. The Maxwell–Kohn–Sham equations are solved by projecting out non-physical gauge degrees of freedom and thus symplectic geometry and Hamiltonian formulation is regained. In addition, I will briefly discuss the prerequisites for TDDFT Calculator interface to ASE, such way that one considers all the degrees of freedom of the light-matter system: nuclei, light and electrons, with Hamiltonian formalism, in both DFT and TDDFT.