Thermodynamic electrophilicity.

We revisit the electrophilicity index proposed by Parr et al., with special emphasis on the working equations used to calculate this descriptor. We show that the standard way to obtain this reactivity index (using the conceptual density functional theory formalism) leads to several issues. In this contribution, we propose to overcome these difficulties by making use of the finite temperature grand-canonical formalism. In this way, we not only bypass the characteristic inconsistencies of the zero temperature formulation but we are able to obtain a simple exact working equation for the electrophilicity in terms of electronic structure magnitudes.