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According to density functional theory (DFT), the information contained in the electron density should suffice to determine any molecular property in the ground state. To most people, however, DFT is merely a computational approach. It was Robert G. Parr, my Ph.D. advisor, who pioneered the effort to appreciate and quantify molecular structure, bonding, and reactivity properties in DFT language. The theoretical framework that he established is called Conceptual DFT, where electronegativity, hardness/softness, and Fukui function can be rigorously formulated, as outlined in his book with Weitao in 1989, reviewed by myself in 2009, and summarized in the book that I edited in 2022.

Our new approach is different. We propose to employ simple density functionals such as Shannon entropy, Fisher information, Pauli energy, etc., for the purpose. Recent examples of our work include applying them to quantify

  1. Steric effect, steric charge, and stereoselectivity,
  2. Strong covalent interactions,
  3. Electrophilic/nucleophilic regioselectivity,
  4. Cooperativity, frustration, and homochirality.

We also worked on appreciating such chemical concepts as homochirality, aromaticity, acidity, ortho/para/meta group directing effect, anomeric effect, and generalized anomeric effect using this idea. Pleas see a recent review and topic collection for more details.

This endeavor is called Information-Theoretic Approach. My long-term goal is to develop a density-based reactivity theory.