*Advanced*

`iord`

Order of the approximation used in module **genfmt**. FEFF uses
order 2 by default, which is correct to terms of order ,
and corresponds to 6x6 scattering matrices in the Rehr-Albers
formalism. Single scattering is calculated exactly to this order.
The 6x6 approximation is accurate to within a few percent in every
case we have tried (that is, higher order doesn't change the result
more than a few percent). However
shells and
higher shells may require increased iorder for coupling the matrix
elements. Changing the default values requires some familiarity
with the Rehr-Albers paper and the structure of the module **genfmt**.
To do so, follow the instructions in the FEFF source code in
subroutine `setlam`. The key `iord` is passed to
`setlam` for processing. You may need to change the code
parameter `lamtot` if you want to do higher order
calculations. For details of the algorithm used by **genfmt**, see the
paper by J.J. Rehr and R.C. Albers
. For the
and higher edges, you may receive an error
message like: `Lambda array overfilled`. In that case the
calculations should be repeated with IORDER -70202 (10x10 matrices).
* change iorder for M4 calculations
IORDER -70202