We investigated the convergence of the core-ionization energy with respect to the embedding space for various molecules using the DMET-IP-CVS-EOM-CC method. We also elucidated the convergence with respect to basis sets. Following these assessments, we showcased the performance of the DMET-based methods for a molecular set consisting of 21 amino acids. Regarding the convergence with respect to the embedding space, we systematically increased the number of atoms in the embedding space. As shown in Fig. , including the first-nearest-neighbor heavy atoms plus all attached hydrogens within the embedding space led to convergence of the core-ionization energy within 0.05 eV of the IP-CVS-EOM-CC methods.