Projector-Based Quantum Embedding for Molecular Systems: An Investigation of Three Partitioning Approaches

Projector-based embedding is a relatively recent addition to the collection of methods that seek utilize chemical locality provide improved computational efficiency. This work considers interactions between different proposed procedures for this method and their effects on accuracy results. The interplay embedded background, projector type, partitioning scheme, level atomic orbital (AO) truncation are investigated selection reactions from literature. Huzinaga projection approach proves be more reliable than level-shift when paired with other procedural options. Active subsystem projected AO decomposition (SPADE) procedure slightly better combination Pipek–Mezey localization Mulliken population screening (PMM). Along these two options, new criteria based von Neumann entropy related occupancy. overlaps previous PMM method, but process computationally simpler. Finally, robust option tested systems projection, satisfactory results being acquired at even most severe level.