EXAFS as a tool for bond length determination in the environment of heavy atoms

The scattering amplitude of a heavy atom structure is generated mainly by the contribution of the heavy scatterers, because the scattering amplitude is proportional to the electron density. In the case of a low scattering part of light atoms this may lead to incorrect calculation of atomic coordinates. Is the structure model similar to correct structure, then it is very difficult to find an independent criterion for the accuracy of the bond lengths.