2020/10/18 by Giulia M. Bovolenta, S. Bovino, Bovolenta, Giulia +9 · 1 citation
Chemistry · Earth and Planetary Sciences · Physics and Astronomy · #Astrophysics and Star Formation Studies #Astrophysics of Galaxies (astro-ph.GA) #Atmospheric Ozone and Climate #FOS: Physical sciences #Molecular Spectroscopy and Structure
paper · pdf · doi:10.48550/arxiv.2010.09138
openalex publication_date 2020/10/18 · openalex created_date 2022/07/25 · openalex updated_date 2026/07/28
The knowledge of the binding energy of molecules on astrophysically relevant\nices can help to obtain an estimate of the desorption rate, i.e. the molecules\nresidence time on the surface. This represents an important parameter for\nastrochemical models, crucial to determine the chemical fate of complex organic\nmolecules formed on dust grains and observed in the densest regions of the\ninterstellar medium. In this work, we propose a new robust procedure to study\nthe interaction of atoms and molecules with interstellar ices, based on\n\ab initio molecular dynamics and density functional theory, validated\nby high-level \ab initio methods at a CCSD(T)/CBS level. We have\napplied this procedure to hydrogen fluoride (HF), a promising tracer of the\nmolecular content of galaxies. In total we found 13 unique equilibrium\nstructures of HF binding to small water clusters of up to 4 molecules, with\nbinding energies ranging from 1208 to 7162 K. We computed a 22-molecules model\nof amorphous solid water (ASW) surface using \ab initio molecular\ndynamics simulations and carried out a systematic analysis of the binding sites\nof HF, in terms of binding modes and binding energies. Considering 10 different\nwater clusters, we found a binding energy distribution with an average value of\n5313\±74 K, and a dispersion of 921\±115 K. Finally, the effect of the\nelectrostatic field of the 22 water molecules on the binding energies was\ninvestigated incrementally by symmetry adapted perturbation theory, in order to\ngauge the effect of the water environment. The results indicate that the extent\nof the electrostatic interaction of HF with ASW depends strongly on the\nproperties of the binding site. We expect that this work will provide a solid\nfoundation for a systematic development of a binding energy distribution\ndatabase of molecules on interstellar surfaces.\n