Fig. 2

Cluster free energy differences between spin states for the GR clusters. GR2 × 6(− 5): from left to right are spin states with unpaired electrons from 1 to 33 (i.e., 1, 3, 5…). GR2 × 6(− 6), GR3 × 6(− 10) and GR4 × 6(− 9): from left to right are low, intermediate and high spin states respectively. For all models, the energies of the highest spin states are set to be 0