As a second test case for rPT2, we consider the widelystudied example of the chromium dimer (Cr 2 ) in its 1 Σ + g ground state. 9,10,39,126-136 is system is notoriously challenging as it combines dynamic and static correlation e ects hence requiring multi-con gurational methods and large basis sets in order to have a balanced treatment of these two e ects. Consequently, we compute its ground-state energy in the cc-pVQZ basis set with an internuclear distance R Cr-Cr = 1.68 Å close to its experimental equilibrium geometry. Our full-valence calculation corresponds to an active space CAS (28,198) and the computational protocol is similar to the previous example. e second-order corrected value E (0) + E as well as its renormalized version E (0) + ZE as a function of the number of determinants in the reference wave function are reported in Table and depicted in Fig. . Here also, we observe that rPT2 is clearly a superior extrapolation framework compared to the standard PT2 version as it yields a much straighter extrapolation curve, even in the case of a strongly correlated system such as Cr 2 . e renormalization factor Z [see Eq. ( )] mitigates strongly the overestimation of the FCI energy for small wave functions by damping the second-order energy E . Linear extrapolations of the PT2 and rPT2 energies based on the two largest wave functions yields extrapolated FCI energies of -2087.734 and -2087.738, respectively (see also Table ). e di erence between these two extrapolated FCI energies provides a qualitative idea of the extrapolation accuracy.