Using K Pre-Edge XAS to Follow Spin Transition in |Fe3+|
========================================================

The following tutorial shows how changes in the X-ray absorption spectrum
at the
K pre-edge, resulting from 1s to 3d transitions, can be used to track the spin
state of |Fe3+| compounds.

1. Write down the electronic configuration of |Fe3+|. Show that there are two
ways to fill the 3d orbitals, leading to a high spin (S = 5/2) and a low spin
ground state (S = 1/2).

2. Run two K pre-edge calculations for |Fe3+| in an octahedral crystal field,
one with 10Dq set to 2.0 eV and 3.3 eV. What differences do you observe between
the two spectra? Based on the two calculations what can you say about the spin
state of |Fe3+| in the experimental spectrum below.

.. figure:: assets/westre_fig2.png
    :width: 60 %
    :align: center

    Westre et al., J. Am. Chem. Soc., 1997, 119 (27), 6297--6314.

3. Change the 10Dq value from 2.6 to 3.6 eV in steps of 0.1 eV. At what value
do you observe the spin transition?

4. Is it possible to induce a low spin to high spin transition by changing the
scaling factors of the Slater integrals while keeping the 10Dq set to 3.3 eV?

.. |Fe3+| replace:: Fe\ :sup:`3+`\