Atomic Radii for Depicting Atoms in a Molecule

The effective atomic radius imaging the atoms in an equilibrium molecular structure is discussed for He, Ne, Ar, Kr, and Xe, based on the electrostatic field calculated with the Hartree-Fock and configuration interaction singles and doubles methods, both with and without the Douglas-Kroll-Hess relativistic transformation. The effective atomic radius r is defined as a distance from the nucleus at which the magnitude of the electric field is that in He at one half of the equilibrium bond length of He2. The resulting radii are ca. 20% larger than Bondi's radii, which are conventionally recognized as the van der Waals radii. Valence radii and inner core radii are also defined and discussed.