The electron affinity and ionization potential of the solvated uranyl from the quantum embedding approach

The quantum embedding approach offers an efficient way for large-scale electronic-structure calculations, enabling reductions in computational cost while retaining high-level accuracy. This aspect is particularly crucial for the modeling of actinide solution systems. Here, we present a subsystem approach for predicting valence electron binding energies, including the electron affinity (EA) and the ionization potential (IP) of the solvated uranyl. This approach combines the equation-of-motion coupled cluster method for electron attachment/detachment and the mean-filed treatment via absolutely localized projection-based embedding scheme, using representative structures extracted from ab initio molecular dynamics simulations, together with our newly developed norm-conserving actinide pseudopotentials. Our results show that the EA of solvated uranyl can be well reproduced by using the quantum embedding approach, whereas the IP requires an expanded active high-level region because of its global character. Including the full first solvation shell yields a marked improvement for the IP. This work demonstrates that the accuracy of the embedding partition is determined not only by the apparent structural locality of the system but also by how spatially localized the electronic-structure property of interest is. We anticipate that the quantum embedding approach will provide an efficient route to reducing the computational cost of high-level quantum chemical calculations for complex actinide solution systems.