  The Electron Localization Function (ELF) by Becke and Edgecombe [J. Chem.
Phys. {\bf 92}, 5397 (1990)] is routinely adopted as a descriptor of atomic
shells and covalent bonds. Since the ELF and its related quantities find useful
exploitation also in the construction of modern density functionals, the
interest in complementing the ELF is linked to both the quests of improving
electronic structure descriptors and density functional approximations. The ELF
uses information which is available by considering parallel-spin electron pairs
in single-reference many-body states. In this work, we complement this
construction with information obtained by considering antiparallel-spin pairs
whose short-range correlations are modeled by a density functional
approximation. As a result, the approach requires only a contained
computational effort. Applications to a variety of systems show that, in this
way, we gain a spatial description of the bond in H$_2$ (which is not available
with the ELF) together with some trends not optimally captured by the ELF in
other prototypical situations.
