Simulating the Formation of Carbon-rich Molecules on an idealised Graphitic Surface

TL;DR

This study uses reactive molecular dynamics simulations to explore how complex carbon-rich molecules form on idealized graphitic surfaces under various temperature conditions, revealing the influence of surface interactions and environment turbulence.

Contribution

It provides new insights into the temperature-dependent formation pathways of carbon molecules on astrophysical dust grain analogs, highlighting the role of surface mobility and environmental turbulence.

Findings

Large chains form at 100-500K on surfaces.

Fullerene-like molecules form at 2000-3000K.

Surface interactions slow down coagulation at high temperatures.

Abstract

There is accumulating evidence for the presence of complex molecules, including carbon-bearing and organic molecules, in the interstellar medium. Much of this evidence comes to us from studies of chemical composition, photo- and mass-spectroscopy in cometary, meteoritic and asteroid samples, indicating a need to better understand the surface chemistry of astrophysical objects. There is also considerable interest in the origins of life-forming and life-sustaining molecules on Earth. Here, we perform reactive molecular dynamics simulations to probe the formation of carbon-rich molecules and clusters on carbonaceous surfaces resembling dust grains and meteoroids. Our results show that large chains form on graphitic surfaces at low temperatures (100K - 500K) and smaller fullerene-like molecules form at higher temperatures (2000K - 3000K). The formation is faster on the surface than in the gas at low temperatures but slower at high temperatures as surface interactions prevent small clusters from coagulation. We find that for efficient formation of molecular complexity, mobility about the surface is important and helps to build larger carbon chains on the surface than in the gas phase at low temperatures. Finally, we show that the temperature of the surface strongly determines what kind of structures forms and that low turbulent environments are needed for efficient formation.