As expected, the CI-truncation error is dependent on the distance. The closer the benzenes are to each other, the more charge transfer configurations are required for an accurate description of the correlation effects. At an inter-fragment distance of 4.5 Å and above, disconnected spaces suffice to have deviations smaller than 1 kcal mol -1 from the corresponding Stochasti-CASSCF calculation. Notice that this is a typical distance for π-stacking, leading to the conclusion that highly truncated MC wave functions, such as GAS wave functions with disconnected spaces, can be of high value for realistic model systems of weakly interacting fragments. It has to be emphasized that the mean field orbital relaxation effect of fragments onto each other is still accounted for by the SCF procedure, even for disconnected spaces, as opposite to methods where only the CI problem is solved in a fixed MO basis.