New relativistic atomic ground-state wave functions calculated by using the Dirac–Fock program package GRASP92 [Parpia et al. (1996). Comput. Phys. Commun. 94, 249–271; Su & Coppens (1997). Acta Cryst. A53, 749–762, (1998). Acta Cryst. A54, 357] for atoms H through Kr (Z = 1–36) have been fitted by a linear combination of Slater-type functions using a nonlinear least-squares procedure. These analytical expressions allow derivation of closed-form expressions for the X-ray scattering factors of the core and valence electrons and for the atomic densities and electrostatic properties of the pseudoatoms, the latter being required for the evaluation of physical properties from accurate X-ray diffraction data. All results are accessible via https://wings.buffalo.edu/~chem9982.