Weak Interaction Network in N₂O₄/HNO₃/H₂O Corrosive Microenvironments: A Quantum Chemical Mapping.

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Materials Science

Background:

• Understanding weak interactions in propellant systems like N2O4/HNO3/H2O is crucial for predicting stability and reactivity.
• Nitric acid (HNO3) and dinitrogen tetroxide (N2O4) are key components in some rocket propellants, and their interactions influence system performance and safety.
• Corrosion in propellant systems is a significant concern, and identifying its origins, including potential ion formation mechanisms, is vital.

Purpose of the Study:

• To computationally investigate the weak interaction networks within N2O4/HNO3/H2O and HNO3/N2O4 propellant systems.
• To elucidate the role of water and HNO3 in stabilizing or destabilizing these propellant mixtures.
• To explore novel pathways for ion formation in these systems, potentially explaining corrosion mechanisms.

Main Methods:

• Quantum chemical calculations were employed to map interaction networks.
• Electrostatic potential analysis was used to quantify hydrogen bond strengths.
• Solvation models were utilized to assess interactions in a liquid N2O4 environment.

Main Results:

• Nitric acid (HNO3) was identified as the dominant hydrogen bond donor, forming strong complexes with water (H2O).
• Water acts as a polarization catalyst, enhancing stabilization in ternary HNO3···N2O4···H2O clusters.
• In water-depleted conditions, a double proton transfer pathway was predicted in 2HNO3···N2O4 clusters, leading to the formation of ion pairs ([HNO2···NO2+]···NO3-).

Conclusions:

• The study reveals complex weak interaction networks governing the behavior of N2O4/HNO3/H2O propellants.
• A novel theoretical pathway for ion formation via concerted double proton transfer in low-water environments was proposed.
• These findings offer new insights into potential ion sources contributing to corrosion in propellant systems.