SPIN

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    ispin [x y z]

This card is used to specify the type of spin-dependent calculation for spin along the (x, y, z) direction, along the z-axis by default. The SPIN card is required for the calculation of all spin-dependent effects, including XMCD and SPXAS .

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 parameter nspx=1 (default), the values of the index ispin correspond to the following calculations:

Table 2.3: Allowed values of the ispin argument of the SPIN card.
ispin     meaning
2 spin-up SPXAS and $\ell $DOS
$-2$ spin-down SPXAS and $\ell $DOS
1 spin-up portion of XMCD calculations
$-1$ spin-down portion of XMCD calculations


The default ispin=0 is used for spin-independent 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. 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)
  SPIN 1
  XMCD

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
  POTENTIALS
  *  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       4.0     (a sublattice)     up
      2   26   Fe    2      3     3      -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