Energy components in energy decomposition analysis (EDA) are path functions; why does it matter?

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Chemical Bonding Theory

Background:

• Bond Dissociation Energy (BDE) is a state function, providing a well-defined measure of bond strength.
• Energy Decomposition Analysis (EDA) is widely used to dissect chemical bond energies into components like electrostatic, Pauli, and orbital interactions.
• The interpretation of EDA results is crucial for understanding the nature of chemical bonds (e.g., ionic vs. covalent).

Purpose of the Study:

• To clarify the nature of EDA energy components as path functions.
• To evaluate the reliability of EDA for precise chemical bond characterization.
• To highlight inconsistencies between standard EDA pathways and established chemical bonding principles.

Main Methods:

• Theoretical discussion of state functions versus path functions in chemical thermodynamics.
• Analysis of the mathematical and conceptual implications of EDA pathway dependence.
• Comparison of EDA outcomes with fundamental chemical bonding knowledge.

Main Results:

• EDA energy components (electrostatic, Pauli repulsion, orbital interaction) are identified as path functions, not state functions.
• The magnitudes of EDA components are dependent on the chosen computational pathway, leading to non-unique results.
• Standard EDA pathways can yield conclusions inconsistent with accepted chemical bonding models, even for simple molecules.

Conclusions:

• EDA is best suited for comparative analyses of similar chemical bonds (e.g., relative ionic/covalent character).
• Precise, absolute characterization of a specific chemical bond's nature using current EDA methodologies is problematic.
• The arbitrary nature of commonly used EDA pathways necessitates caution in interpreting their results, especially when they contradict established chemical intuition.