inters vtot

The construction of the interstitial potential and density may be changed by using this card. $\mathtt{inters} = \mathtt{ipot} +
2*\mathtt{irav} + 6*\mathtt{irmt}$. ipot=1 might be useful when only the surroundings of the absorbing atom are specified in `feff.inp'. irmt and irav are described only for completeness, and use of nonzero values is strongly discouraged.

potential index. ipot defines how to find the interstitial potential. ipot=0 (default): the interstitial potential is found by averaging over the entire extended cluster in `feff.inp'. ipot=1 : the interstitial potential is found locally around the absorbing atom.

also changes how the interstitial potential is found. irav=0 (default): the equation for V$_int$ is constructed at rav=rnrm. irav=1 : at rav=(rmt +rnrm)/2. irav=2 : at rav=rmt, where rmt is the muffin-tin radius and rnrm is the Norman radius. irmt apparently does not exist in the code

irmt=0 (default): Norman prescription for mt radii. irmt=1 : Matching point prescription for mt radii (do not use).

the volume per atom normalized by ratmin$^3$ (vtot=(volume per atom)/ratmin$^3$), where ratmin is the shortest bond for the absorbing atom. This quantity defines the total volume (needed to calculate the interstitial density) of the extended cluster specified in `feff.inp'. If vtot $\leq0$ then the total volume is calculated as a sum of Norman sphere volumes. Otherwise, $total\ volume = \mathtt{nat} * (\mathtt{vtot}*\mathtt{ratmin}^3)$, where nat is the number of atoms in an extended cluster. Thus vtot=1.0 is appropriate for cubic structures, such as NaCl. The INTERSTITIAL card may be useful for open systems (e.g. those which have ZnS structure).

  * improve interstitial density for ZnS structures.
  * vtot = (unit_cell_volume/number_of_atoms_in_unit_cell)/ratmin**3)=1.54