Conceptual Density Functional Theory under Pressure: XP-PCM Method Applied to Atoms

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Since its conception, the field of Conceptual Density Functional theory has succeeded in giving rigid definitions to previously vaguely defined chemical concepts such as the electronegativity and the chemical hardness. Within this field, the energy is expanded as a functional of the number of electrons and the external potential and its resulting descriptors have proven their usefulness in retrieving chemical properties and scrutinizing chemical reactivity. In recent years, extensions to this framework are at stake by including external perturbations such as electric fields, magnetic fields, temperature and mechanical forces. By using the XP-PCM (eXtreme Pressure Polarizable Continuum Model) method, developed by Cammi et al. to simulate extreme pressures on the single molecular level, now pressure is introduced into this new set of perturbations and its influence on reactivity descriptors in the conceptual DFT framework can be evaluated. This with the aim of describing and better understanding electronic structure and molecular reactivity in the GPa pressure range.

By applying XP-PCM and conceptual DFT to atoms of the main group elements elements hydrogen to krypton, the first order response function with respect to the pressure is identified as the electronic volume. The derived electronic radii correlate well with known sets of atomic radii, indicating it as a valid measure of the system extension. This interpretation allows to explain the trends observed for the ionization potentials, electron affinities and electronegativity, all decreasing under pressure. Additionally, the atom-based model used here, succeeds in retrieving some striking findings in high pressure chemistry. The chemical hardness on the other hand was found to increase with pressure and its inverse cube (i.e. the softness) correlates well with the isotropic polarizability for different elements under pressure.

Finally, as a local descriptor, the electron density is analysed under pressure, finding a clear translocation of electron density from the peripheral to the internal regions of atoms. Three different analysis methods, including two rooted in information theory, all find unbiased periodic behavior in the density of elements under pressure with elements early on in a period displaying a more sensitive response to external pressure than their later counterparts.
Original languageEnglish
Number of pages1
Publication statusPublished - 23 Jun 2022
Event12th Congress on Electronic Structure: Principles and Applications - Vigo, Spain
Duration: 21 Jun 202224 Jun 2022


Conference12th Congress on Electronic Structure: Principles and Applications
Abbreviated titleESPA2022
Internet address


  • conceptual density functional theory
  • high pressure chemistry
  • XP-PCM


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