Modeling the diffraction process of molecular crystals: computation of X-ray scattering intensities from ab initio electron densities

An algorithm for calculating the scattering factors of atomic fragments in molecules as defined by the Stockholder recipe is presented. This method allows the calculation, from ab initio molecular wave functions, of structure factors including individual anisotropic atomic temperature factors. These structure factors agree with the model used in most least-squares multipole-refinement procedures. Calculations on the H₂O molecule illustrate the method.