Table 1. RMSDs^b (in Å) of Different QM/MM-Optimized Geometries Compared to the Experimentally Determined X-ray Structure^a,27.

structure and spin	57-atom QM region	181-atom QM region
[V-CO3]2–, MS = 3/2	0.082	0.079
[V-CO3]−, MS = 1	0.085	0.079
[V-CO3]−, MS = 2	0.111	0.104
[V-CO3], MS = 3/2	0.104	0.091
[V-NO3]−, MS = 3/2	0.095	0.085
[V-NO3], MS = 1	0.095	0.082
[V-NO3]+, MS = 3/2	0.093	0.088

^aThe BS7-235 solution is used for all calculations.

^bThe RMSD is defined as the deviation of the [VFe₇S₈C(XO₃)] part with respect to both cofactors in the X-ray structure.