# Mapping the structural diversity of C60 carbon clusters and their infrared spectra

## TL;DR

This study computationally explores the structural diversity and infrared spectra of C60 carbon clusters, identifying specific structural families and their potential relevance to astronomical IR observations.

## Contribution

It introduces a comprehensive computational framework to analyze the structure-spectra relationship in C60 isomers, linking specific structures to observed IR features in space.

## Key findings

- Cage structures are likely responsible for IR plateau in 6-9 micron range.
- Four main structural families of C60 are identified: cages, planar polycyclic aromatics, pretzels, and branched.
- Only cage family matches the astronomical IR spectra features.

## Abstract

The current debate about the nature of the carbonaceous material carrying the infrared (IR) emission spectra of planetary and proto-planetary nebulae, including the broad plateaus, calls for further studies on the interplay between structure and spectroscopy of carbon-based compounds of astrophysical interest. The recent observation of C60 buckminsterfullerene in space suggests that carbon clusters of similar size may also be relevant. In the present work, broad statistical samples of C60 isomers were computationally determined without any bias using a reactive force field, their IR spectra being subsequently obtained following local optimization with the density-functional-based tight-binding theory. Structural analysis reveals four main structural families identified as cages, planar polycyclic aromatics, pretzels, and branched. Comparison with available astronomical spectra indicates that only the cage family could contribute to the plateau observed in the 6-9 micron region. The present framework shows great promise to explore and relate structural and spectroscopic features in more diverse and possibly hydrogenated carbonaceous compounds, in relation with astronomical observations.