Our calculations allow us to interpret the spin-crossover phenomena in this dimer more concretely. Firstly, we propose that the magnetic moment at high temperature arises from a mixture of S = 2 and S = 1 dimers in different polymorphs or crystallites. More specifically, the magnetic moment arises from the four singly occupied orbitals arising from the dz 2 , dxy, and dx 2 -y 2 Cr orbitals (See Figure ). We note that for the geometry of the S = 2 dimer at 290 K, it is not possible to localize these four singly occupied orbitals into two pairs centered on the two chromium nuclei, because the dxy and dx 2 -y 2 orbitals are both symmetric linear combinations of the chromium d orbitals.