Kotani plots

Fig. 20.23 Kotani plot for a configuration A is the spin-orbit coupling constant. Typical values of /i .ff(298 K) for Cr(II), Mn(III), Ru(IV) and Os(IV) are indicated on the curve.

We can now plot the value of (given by the positive square root of the above expression) against x, or, more conveniently, against 1/x, to give a so-called Kotani plot. This has been done in Fig. 9.3. Also on this figure are indicated the values of C/kT for some d ions at 300 K, C being given the... 

Fig. 9.3 A Kotani plot for the t g configuration together with 300 K values for some ions. The spin-only formula gives === 1-73 whereas first row transition metal ions roughly approximate to this value at room temperature, values for second and third row ions can be very different.

Fig. 9.4 (a) A simple Kotani plot for [VCIg] " (C = 190 cm" ). (b) A Kotani plot including best-fit tetragonal distortions and orbital reduction factors. In both cases experimental data are given as dots. 

As we have seen, this relationship holds quite well for the first row transition series. For the second and third row elements it gives totally misleading results because the spin-orbit coupling of these ions is much greater than /cT—so that, usually, the plateau of the Kotani plot has not been reached. 

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