The effect of cluster size on the intra-cluster ionic polymerization process

Estefania Rossich Molina, Tamar Stein*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Polyaromatic hydrocarbons (PAHs) are widespread in the interstellar medium (ISM). The abundance and relevance of PAHs call for a clear understanding of their formation mechanisms, which, to date, have not been completely deciphered. Of particular interest is the formation of benzene, the basic building block of PAHs. It has been shown that the ionization of neutral clusters can lead to an intra-cluster ionic polymerization process that results in molecular growth. Ab-initio molecular dynamics (AIMD) studies in clusters consisting of 3–6 units of acetylene modeling ionization events under ISM conditions have shown maximum aggregation of three acetylene molecules forming bonded C6 H6+ species; the larger the number of acetylene molecules, the higher the production of C6 H6+. These results lead to the question of whether clusters larger than those studied thus far promote aggregation beyond three acetylene units and whether larger clusters can result in higher C6 H6+ production. In this study, we report results from AIMD simulations modeling the ionization of 10 and 20 acetylene clusters. The simulations show aggregation of up to four acetylene units producing bonded C8 H8+. Interestingly, C8 H8+ bicyclic species were identified, setting a precedent for their astrochemical identification. Comparable reactivity rates were shown with 10 and 20 acetylene clusters.

Original languageAmerican English
Article number4782
Issue number16
StatePublished - 7 Aug 2021

Bibliographical note

Publisher Copyright:
© 2021 by the authors. Licensee MDPI, Basel, Switzerland.


  • Ab-initio molecular dynamics
  • Acetylene
  • Ben-zene
  • Interstellar medium
  • Ion–molecule reactions’ astrochemistry
  • Molecular growth
  • Polycyclic aromatic hydrocarbons
  • Van der Waals clusters


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