Atomic Reactivity Descriptors from Conceptual DFT under Isotropic Pressure

Since its conception, the field of Conceptual Density Functional Theory has aimed at giving rigorous definitions to chemical concepts and identifying useful response functions. Next to the traditional expansion in N and v, extensions to this framework are at stake in recent years by including external perturbations. By using the XP-PCM (eXtreme Pressure Polarizable Continuum Model) method, the influence of isotropic pressure on the response functions in the conceptual DFT framework can be evaluated with the aim of describing and understanding electronic structure under pressure.
By applying XP-PCM and conceptual DFT to atoms of the main group elements from hydrogen to krypton, an electronic volume could be identified and the derived electronic radii correlate well with known sets of atomic radii. This interpretation allows to explain the trends observed for the electronegativity and its components, all decreasing under pressure. The chemical hardness was found to increase with pressure and its inverse cube (i.e. the softness) correlates well with the isotropic polarizability for different elements.
Finally, as a local descriptor, the electron density is analyzed under pressure, finding a clear translocation of electron density from the peripheral to the internal regions of atoms. Three different analysis methods, including one from information theory, all find unbiased periodicity in the density of pressurized atoms with elements early on in a period displaying a more sensitive response to external pressure than their later counterparts.