Accelerating Realtime TDDFT with Block-Orthogonalized Manby-Miller Embedding Theory.

Realtime time-dependent density-functional theory (RT-TDDFT) is one of the most practical techniques available to simulate electronic dynamics of molecules and materials. Promising applications of RT-TDDFT to study nonlinear spectra and energy transport demand simulations of large solvated systems over long time scales, which are computationally quite costly. In this paper, we apply an embedding technique developed for ground-state SCF methods by Manby and Miller to accelerate realtime TDDFT. We assess the accuracy and speed of these approximations by studying the absorption spectra of solvated and covalently split chromophores. Our embedding approach is also compared with less accurate, less costly QM/MM charge embeddings. We find that by mixing levels of detail the embedded mean-field theory scheme is a simple, accurate, and effective way to accelerate RT-TDDFT simulations.