Figure compares the SPAWN graphs of Gly-Gly dipeptides obtained from DMRG and DFT calculations, including ωB97M-V, B3LYP, and HF methods. Despite the lower-quality wavefunctions in DFT and HF compared to DMRG, the I paq AB patterns from DMRG show remarkable similarity to those from DFT and HF. Figure provides a more quantitative comparison of the I paq AB indices derived from DMRG with those from HF, B3LYP, and ωB97M-V for the Gly-Gly dipeptide. The plots reveal a high degree of alignment between the lower-quality wave functions (DFT and HF) and the highquality DMRG results. We observe a striking correlation between the self-consistent field approaches and the DMRG, in which the I paq AB of the latter is approximately 1.16 times larger than the former across atom pairs. We do observe that Slater determinant wave functions (DFT and HF, upper row) exaggerate differences between single-bond atom pairs with respect to DMRG. The differentiation is between atom pairs involving an H atom (left cluster) and those that do not (right cluster). So, as can be expected, the high-quality DMRG wavefunction consistently identifies a higher correlation between atoms, however, the self-consistent field approaches catch the same trends. This observation opens interesting perspectives from a practitioner's point of view when correlations in peptide systems need to be characterized at a high quantitative level. A further point of scrutiny is reserved for the effectiveness of the pragmatic summation I AB « I paq AB in eq. . For this purpose, we compared I paq AB with exact block-wise MI measures (I pbq AB ) between full blocks of atomic orbitals associated to certain atoms in the context of DMRG. These blocks represent larger subsystems (e.g., atoms) of the molecule, allowing for MI between constituent atoms to be captured. As dipeptide systems are out of computational reach for this study, we focused on the HCN cyanide molecule, which serves as a small yet informative model for testing I paq AB against I pbq AB . DMRG calculations were performed with a bond dimension of 4096 and a modified 6-31G basis set. In a first run, we ordered the orbitals such that the entanglement entropy could be computed between carbon's orbitals (left block) and the remaining NH orbitals (right block). In the subsequent DMRG run, the orbitals were reordered to place nitrogen in the left block to measure MI between nitrogen and the remaining system (CH block). After several reordering, I pbq AB was computed for all atomic connections. Here, we remark that the same information could technically be extracted from a single DMRG run by forming proper traces of subsystems using the obtained MPS wave function, however this becomes computational more demanding for large DMRG bond dimension values (see Ref. ). Figure presents a detailed comparison between I pbq AB (using DMRG) and I paq AB (using DMRG, DFT, and RHF). The figure illustrates the evolution of MI as the hydrogen atom dissociates from the cyanide molecule. By comparing the highly accurate block-wise MI with the more computationally efficient summation method, it is possible to evaluate the effectiveness of summation-based approach of 8 during hydrogen dissociation. The results demonstrate that the summation method captures key trends in MI behavior with a reasonable degree of accuracy. This shows that I paq AB derived from the summation approach reliably approximates the qualitative MI between atoms for such weakly correlated systems, making it a practical solution for larger molecular systems where full DMRG calculations are computationally prohibitive. For a more rigorous and computationally demanding theory on multi-orbital correlations based on concepts of k-partitionability and k-produciblity, we guide interested readers to Ref. . We extended the analysis to compare I pbq AB and I paq AB in the formaldehyde system. Figure displays SPAWN plots for both cyanide and formaldehyde systems, illustrating the MI between atoms, calculated at the DMRG level of theory. Figure A final note concerns the basis dependence and absolute scale of the presented AMI. As it is challenging to associate a direct experimental observable to AMI, it is difficult to assign meaning to their absolute values. Nevertheless, it can be intuitively understood that entanglement and mutual information measures will be proportional to the size of the Hilbert space. For this reason, we investigate the impact of basis set size on I paq AB , by analyzing the CysGly dipeptide system using the correlationconsistent valence X-Zeta (cc-pVXZ) basis set series. The cc-pVXZ basis sets were chosen for their systematic and consistent expansion of basis functions, which allowed us to observe how I