Absolutely Localized Open-shell WF-in-DFT Huzinaga Embedding

While density functional theory (DFT) is often seen as the go-to for quantum mechanical calculations on chemical systems, current implementations have several well known deficiencies. More robust wave function (WF) methods can provide higher accuracy, but that accuracy comes at a significant computational cost. Quantum embedding methods provide a strategy for performing highly accurate calculations on chemical systems while not incurring high computational cost. By dividing a system into absolutely localized subsystems -- described by only the basis functions of the subsystem atoms -- we can significantly reduce the overall computational cost. Huzinaga projection operator based absolute localization wavefunction embedded in DFT (WF-in-DFT) energy differences recreate those of full system WF results across a diverse test set. Recently, we have developed an open-shell embedding extension to the method which can recreate CCSD(T) transition metal spin-splitting energies to within 1 kcal/mol for a fraction of the computational cost.