Additionally, we employed the frozen core (FC) approximation to solve the ground state CCSD equation. Specifically, the "frozen-core CVS" was employed to tackle the EOM-CC equations, which has better accuracy than the CVS scheme, as shown by Vidal et al. This improvement can be attributed to error cancellation, as discussed by Martinez et al. DMET permits the application of any given quantum chemistry method to a fragment of an extended systems by performing a Schmidt decomposition of a low-level (i.e., Hartree-Fock) wave function of the whole system. The Schmidt decomposition generates an embedding subspace of orbitals that contains the user-specified fragment, is unentangled to the rest of the molecule, and is occupied by an integer number of electrons. The number of orbitals in the embedding subspace is of the same order of magnitude as the number of orbitals in the user-specified fragment. Here, the fragments consist of the atom that is core-ionized, plus up to nth nearest-neighbor non-hydrogen atoms with varying n, and all hydrogen atoms attached to those heavy atoms.