On the thermodynamic stability of polycations

Area of Science:

• Computational Chemistry
• Theoretical Chemistry
• Physical Chemistry

Background:

• Understanding the stability limits of charged molecules (polycations) is crucial in various chemical and physical processes.
• Predicting the point at which a molecule will fragment due to excessive charge requires accurate energetic calculations.
• Existing methods may be computationally intensive or lack general applicability across different molecular systems.

Purpose of the Study:

• To develop a simple yet effective approximation for determining the maximum stable charge a molecule can hold.
• To provide a theoretical framework for predicting polycationic stability using fundamental molecular properties.
• To analyze the relationship between molecular size and its maximal charge capacity.

Main Methods:

• The approximation utilizes ionization potentials and electron affinities of parent and fragment species.
• It incorporates the neutral parent molecule's dissociation energy as a key parameter.
• Analytical phase diagrams of polycationic stability are derived by parameterizing these energetic quantities.

Main Results:

• The proposed approximation successfully estimates the largest charge a molecule can sustain before fragmentation.
• Phase diagrams illustrating polycationic stability were generated, showing clear trends.
• The maximal charge capacity was found to be dependent on the size of the molecular system.

Conclusions:

• The developed approximation offers a computationally efficient way to assess polycation stability.
• This method is broadly applicable, as demonstrated by numerical examples with linear polyenes, annulenes, and helium clusters.
• The findings provide valuable insights into the fundamental limits of molecular charge storage.