The most notable difference between ASD-DMRG and conventional DMRG, is the low value of M at the order of 10 2 that is required by ASD-DMRG to reach convergence for fragment-like systems. Conventional ab-initio DMRG, where the sites are not optimized fragments but spatial molecular orbitals requires M values that are approximately two orders of magnitude higher. In Reference 77, the authors of ASD-DMRG state that: "If a poor initial guess for the chain includes only neutral fragments and the total charge is constrained to be neutral, the algorithm will keep only neutral fragment states although charge transfer configurations may be important in the exact ground state" and overcome this limitation via a perturtative correction. Within the GAS approach, charge transfer configurations are added by tuning the number of interspace excitations, n exc . It is thus, possible to precisely identify these configurations and quantify their importance, as shown in Figure .