# Electric Fields Can Assist Prebiotic Reactivity on Hydrogen Cyanide Surfaces

## TL;DR

Electric fields on hydrogen cyanide surfaces may help form important prebiotic molecules in cold environments like Titan's atmosphere.

## Contribution

The study reveals how electric fields on HCN surfaces can enable low-temperature catalytic reactions relevant to prebiotic chemistry.

## Key findings

- HCN nanocrystal tips have polar facets with strong electric fields.
- Field-assisted mechanisms can enable HNC formation from HCN at low temperatures.
- These reactions may explain the presence of HNC in cold environments like Titan.

## Abstract

Hydrogen cyanide
(HCN) is present in many astrochemical environments,
including interstellar clouds and comets. On Saturn’s moon
Titan, large amounts of HCN ice are present in the atmosphere and,
following surface deposition, may influence both chemical and geological
evolution. However, despite HCN’s relevance to origin of life
chemistry, the physiochemical properties of its solid state remain
poorly characterized. For example, the crystals of HCN exhibit a range
of rare properties, including pyroelectricity, and the ability to
glow and jump under certain conditions. Here we use quantum chemical
methods to predict HCN crystal surface energies, from which we derive
the needle-like, high-aspect-ratio morphology of HCN nanocrystals.
The predicted tips expose high-energy polar facets imbued with strong
electric fields. We suggest that the combination of tips of opposite
polarity helps to explain the cobweb-structure of solid HCN, and that
fracture can transiently expose energetic surfaces, capable of catalysis
at low temperature. One such process is predicted to be the near-barrierless
formation of isocyanide (HNC) on HCN crystals, following proton addition
or abstraction, for example, via radiation or acid/base-chemistry.
Such field-assisted surface mechanisms may contribute to HCN-to-HNC
isomerization under relevant conditions, and are suggested to explain
part of the out-of-equilibrium abundance of HNC in cold environments
such as Titan’s atmosphere, and, potentially, in cometary comae.