# INTERSTITIAL

INTERSTITIAL inters totvol


The construction of interstitial potential and density may be changed by using this card. inters = ipot + 2*irav + 6*irmt. ipot=1 might be useful when only the surroundings of the absorbing atom are specified in ‘feff.inp’. irav and irmt are described only for completeness and nonzero values are strongly not recommended.

ipot
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.
irav
also changes how interstitial potential is found. irav=0 (default): equation for Vint is constructed at rav=r_nrm. 1 : at rav=(r_mt+r_nrm)/2 , 2 - at rav=r_mt
irmt
irmt=0 (default): Norman prescription for mt radii. irav=1 : Matching point prescription for mt radii (do not use)
totvol
is the volume per atom normalized by ratmin3 (totvol=(volume per atom)/ratmin3), where ratmin is the shortest bond for the absorbing atom. This quantity defines the total volume (needed to calculate interstitial density) of the extended cluster specified in ‘feff.inp’. If totvol $\leq$ 0 then the total volume is calculated as a sum of norman sphere volumes. Otherwise, totalvolume = nat * (vtot * ratmin3); where nat is a number of atoms in an extended cluster. Thus totvol=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.
* totvol = (unit_cell_volume/number_of_atoms_in_unit_cell)/ratmin**3)=1.54
INTERSTITIAL 0 1.54