Accurate elastic scattering factors for lithium to argon based on correlated wavefunctions

Elastic scattering factors (or atomic form factors) f (s) for Li to Ar have been derived in the first Born approximation from ab initio MR-SDCI (multireference singly and doubly excited configuration interaction) calculations which recover between 90 and 99% of the estimated total correlation energy. The correlation effects on f (s) are contrasted with the relativistic effects known from the literature. Atomic form factors are presented that take into account correlation and relativistic contributions in an additive manner.