Spin State Diagrams of 3dn Cations in Tetragonally Distorted Octahedral Sites

The possible existence of an intermediate spin state is now a few decades fascinating solid state chemists and physicists, experimentalists, and theoreticians. In this article, we revise some recent results on the stability diagrams of spin states, low, high, or intermediate, in distorted environments and extend their approach to redraw more realistic diagrams for d4, d5, and d6 ions in a tetragonally distorted 6-fold oxygen environment (D4h, D2d, and C4ν). The model relies on a point charge model and further uses effective parameters to account for the cubic field drift on spin state change and for suitable values for solid state of the expectation values of the 3d-radial wave functions; additionally the model uses rational parameters to characterize the distortion; finally, we also consider the possible existence of states’ combinations to propose reliable stability diagrams. Whatever the representation involved in the distortion, the existence domain of the intermediate spin state appears very small an...