Electron Scattering Factors of Ions and their Parameterization

Elastic electron scattering factors of 106 ions are represented in a parameterized form that separates the diverging Coulomb term due to ionic charge from the finite contribution of the remaining screened atomic field. This parameterization is shown to be very convenient for many-beam analysis of electron diffraction data and numerically more accurate for interpolating the electron scattering factors of ions in the region of small angles of scattering than the conventional methods of interpolation. Absorptive electron scattering factors have also been calculated numerically for a wide range of ions. It is found that these factors differ from those of the corresponding neutral atoms only for small angles of scattering with s < 0.3 Å^-1. For most applications of transmission electron diffraction, the effects of crystal ionicity on the absorptive crystal structure factors may therefore be neglected and the corresponding factors of neutral atoms may be used.