If instead one assumes that every vanadium ion has an oxidation state of +4, the average expected from the nominal chemical formula, the results produce significantly higher difference values for the Ni1/V1 (-0.173), V3 (-0.269), and V4 (+0.739) sites, where the difference is the nominal state minus the bond valence sum. Alternatively, if one believes that the average state of +4 is achieved with only two oxidation states, that would require an even mix of V 3+ and V 5+ because of how strongly the neutron and X-ray diffraction corefinement restricts the stoichiometry. Optimizing BVS results in this case requires more inspection. The best fits for V1 and V4 are 100% V 3+ and 100% V 5+ , respectively, as in the three state case. The +3/+5 fractions for V2 and V3 then must be optimized under the restriction of charge balance for the system. This optimization results in a V2 +3/+5 fractional composition of 0.6545/0.3455 and a difference of 1 × 10 -5 for Ni2/V2. This is an excellent fit, but the corresponding V3 composition of 0.5926 V 3+ /0.4074 V 5+ results in a difference of -0.249, almost twice the difference in the three oxidation state case. When requiring charge balance, there is no mixture of states for V2 and V3 that improves the results for both sites over the three state model. Therefore, since the three state case already describes V2 well and produces a significantly superior V3 fit, it is accepted here as the better description.