The development of the new functional also leads to a new expression for the unpaired electron density. Unpaired electron density is an interpretative tool of quantum chemistry, and the literature already contains multiple definitions with various pros and cons. The new functional form presented here, which is the combination of eqs 5 and 13, has the feature that the density at a point in space is always less than or equal to the density at that point, which is a clearly desirable constraint. This definition of the unpaired electron density may be useful in other contexts as well as for the purpose for which it is used here.