Scattering factor calculations and dispersion corrections for heavy atoms

Abstract

Reliable knowledge of the complex X-ray form factor (Re(f) and Im(f)) is required for crystallography, deformation density bonding studies and refractive index studies. Dispersion corrections are important in DAFS, MAD analyses and XAFS studies. Discrepancies between currently used theoretical approaches of 200% exist for numerous elements from 1 to 3 keV X-ray energies, and at higher energies these discrepancies can persist at the 10% level or more. This has suggested that new formulations and new experimental approaches are necessary. Recent tabulations improve upon the theoretical uncertainty in some of these regions by a factor of 10 and reduce the error of this approach to below one sta..