For the smaller Co/Mg 9 O 9 cluster, truncating the virtual orbital space has a negligible impact on the embedded EOM-EE-CCSD results (see Table ). The state energy differences remain within 100 cm -1 , while the effect on both the SOCC and spin-reversal energy barrier is minimal, staying below 5 cm -1 . These findings are consistent with previous observations for the Co(II)-SMM. The calculated temperature-dependent susceptibilities (χT vs T ) are shown in Figure .