Understanding the connection between electronic structure and material properties is a principal challenge in chemistry and materials science. Useful insights into chemical bonding allow for chemical intuition, which guides and can dramatically accelerate experimental efforts.

We adapt, test and develop chemical concepts for new and challenging conditions — universally applicable descriptors such as atomic radii and electronegativity, and methods for analyzing chemical bonding in molecules and in extended matter. Much of this connects to “Experimental Quantum Chemistry” (EQC), a framework through which the energy of any transformation is described as a sum of terms obtainable interchangeably by computation or experiment.

These concepts are meant to travel — between disciplines, and between thermodynamic regimes that chemists do not usually compare: high pressure, low temperature, and reactions that unfold over geological time. The same descriptors also serve as design tools, guiding the computational search for new materials.

Research Highlights:

• Quantifying Atomic Volume, Partial Charge and Electronegativity in Condensed Phases
  S. Racioppi, P. Hyldgaard, M. Rahm
  J. Phys. Chem. C, 128, 9, 4009–4017, 2024
• A Density Functional Theory for the Average Electron Energy
  S. Racioppi, P. Lolur, P. Hyldgaard, M. Rahm
  J. Chem. Theory Comput. 19, 799–807, 2023
• Electronegativity Equilibration
  F. Sessa, M. Rahm
  J. Phys. Chem. A., 126, 32, 5472–5482, 2022
• In Situ Electronegativity and the Bridging of Chemical Bonding Concepts
  S. Racioppi, M. Rahm.
  Chem. Eur. J. 27, 18156-18167, 2021
• Relating Atomic Energy, Radius and Electronegativity Through Compression
  M. Rahm, P. Erhart, R. Cammi
  Chem. Sci, 12, 2397-2403, 2021
• Electronegativity Seen as the Ground State Average Valence Electron Binding Energy
  M. Rahm, T. Zeng, R. Hoffmann,
  J. Am. Chem. Soc, 141,342-351, 2019 [A new scale of electronegativity]
• Squeezing all Elements in the Periodic Table: Electron Configuration and Electronegativity of the Atoms under Compression, 
  M. Rahm, R. Cammi, N. W. Ashcroft, R. Hoffmann,
  J. Am. Chem. Soc.,141, 10253-10271, 2019 [The Periodic Table at 0-300 GPa]
• Distinguishing Bonds,
  M. Rahm, R. Hoffmann,
  J. Am. Chem. Soc., 138, 3731-3744, 2016 [Introduction to the Q-descriptor, shown in figure]
• M. Rahm, R. Hoffmann, N.W. Ashcroft, Atomic and Ionic Radii of Elements 1-96, Chem. Eur. J. 22, 14625-14632, 2016