  The iron magnetic form factor in SrFe2As2 has been determined by neutron
diffraction and by density functional theory (DFT). As noted previously, the
magnitude of the calculated moment using DFT is sensitive to the Fe-As
distance. However, the shape of the calculated form factor is practically
insensitive to the Fe-As distance, and further we show that the form factor
closely resembles that of bcc iron, and agrees well with experiment. The spin
density exhibits some anisotropy due to geometry and As hybridization.
