Elastic Scattering Amplitudes

From FEFF

All necessary components to obtain the elastic scattering amplitude can be calculated with the FEFF8.2 code. The Thomson scattering amplitudes are written in file ‘fpf0.dat’. Elastic amplitudes near some specific edge are calculated with the DANES card, while those far from the edge are calculated with the FPRIME card, which neglects solid state effects on $f^\prime$ . The $f^{\prime\prime}$ can be obtained with the XANES card. The formula connecting $f^{\prime\prime}$ and the absorption cross section $σ$ is (in atomic units) $f^{\prime\prime}=\omega c \sigma$ . For calculations at energies well above the absorption edge we found that ground state potentials yield better results and that quadrupolar transitions have to be included.