SPIN ispin [x y z]

This card is used to specify the type of spin-dependent calculation. The SPIN card is required for the calculation of all spin-dependent effects, including XMCD and SPXAS. The optional arguments of this card may be used to specify the x, y, and z components of a vector in the direction of the spin. The default is for the spin to point in the z direction. Spin amplitude is specified using the POTENTIALS card (see next paragraph). When the SPIN card is omitted ispin defaults to ispin=0 for spin-independent calculations.

Whenever spin-dependent calculations are made, the spin amplitude and relative spin orientation should be specified in the spinph argument of the POTENTIALS card.

If feff has been compiled with the variable nspx=1 (default), the values of ispin correspond to the following calculations:

Table 2.2: Allowed values of the ispin argument of the SPIN card.
ispin meaning
2 spin-up SPXAS and LDOS
-2 spin-down SPXAS and LDOS
1 spin-up portion of XMCD calculations
-1 spin-down portion of XMCD calculations

If FEFF is compiled with nspx = 2, one simply uses ispin = 1 or ispin = 2 as needed, and the up and down spins are taken care of automatically. See Section 4.4 for more information on the strategies and options available for spin-dependent calculations.

The spin-dependent potentials are calculated from the spin-dependent densities, using von Barth-Hedin results for the uniform electron gas. We use this approximation to construct the spin-dependent muffin-tin potential. This should be fine for EXAFS, where small details of the potential are irrelevant, but may not be good enough in the XANES region, where the self-consistent spin-dependent muffin-tin potential can lead to better results.

* Make spin-up XMCD calculation (XMCD card must also be included)

POTENTIALS card for spin-dependent calculations:

* GdFeO, spin-dependent
* Note that SPIN card must also be present in feff.inp, as well as
* additional cards specific to desired calculations (in this case, XMCD)
* ipot z  tag lmax1 lmax2 xnatph spinph
    0  64  Gd    3     3   0.1     7.0 (c sublattice) up
    1  26  Fe    2     3   2.0     4.0 (a sublattice) up
    2  26  Fe    2     3   3.0    -4.0 (d sublattice) down
    3   8   O    2     3  12.0     0.0 (h sublattice)
    4  64  Gd    3     3   2.9     7.0 (c sublattice) up
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