Electric Fields Can Assist Prebiotic Reactivity on Hydrogen Cyanide Surfaces

Area of Science:

• Astrochemistry
• Materials Science
• Quantum Chemistry

Background:

• Hydrogen cyanide (HCN) is prevalent in astrochemical environments, including Titan's atmosphere.
• Solid HCN's physiochemical properties are poorly understood, despite its relevance to origin-of-life chemistry.
• HCN crystals display unusual properties like pyroelectricity, luminescence, and mobility.

Purpose of the Study:

• To predict the morphology and surface properties of HCN nanocrystals using quantum chemical methods.
• To elucidate the role of HCN solid-state properties in astrochemical processes.
• To explain the observed abundance of isocyanide (HNC) in cold environments.

Main Methods:

• Quantum chemical calculations were employed to predict HCN crystal surface energies.
• Nanocrystal morphology was derived from predicted surface energies.
• Surface energy and electric field effects were analyzed in relation to potential chemical reactions.

Main Results:

• Predicted needle-like HCN nanocrystals with high-aspect-ratio morphology.
• HCN tips expose high-energy polar facets with strong electric fields.
• Fracture can expose energetic surfaces, facilitating low-temperature catalysis, such as near-barrierless HNC formation.

Conclusions:

• The predicted morphology and electric fields of HCN nanocrystals help explain the cobweb structure of solid HCN.
• Field-assisted surface mechanisms on HCN crystals likely contribute to HCN-to-HNC isomerization.
• These mechanisms offer a potential explanation for the out-of-equilibrium HNC abundance in cold astrochemical environments like Titan and comets.