Quantum Chemical Simulations to Unveil the Interstellar Grain Surface Chemistry.
Insights at an Atomistic Scale
A. Rimola,1 J. Enrique-Romero,1,2 S. Ferrero,1 J.A. Luque-Urrutia,1 B. Martínez-Bachs,1 J.
Perrero,1,3 C. Ceccarelli,2 N. Balucani,4 and P. Ugliengo3
1QuantumGrain, Departament de Química, Universitat Autònoma de Barcelona, 08193
Bellaterra, Catalonia, Spain
2Univ. Grenoble Alpes, CNRS, Institut de Planétologie et d'Astrophysique de Grenoble(IPAG), 38000 Grenoble, France
3Dipartimento di Chimica and Nanostructured Interfaces and Surfaces (NIS) Centre,
Università degli Studi di Torino, via P. Giuria 7, 10125, Torino, Italy
4
Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia, Via Elce di Sotto
8, 06123 Perugia, Italy
The Universe is molecularly rich [1]. Its chemical diversity and complexity is reflected by themore than 250 molecular species detected in the gaseous phase by means of radioastronomy[2] and the different solid-state phases in the form of dust grains [3]. The presence of the gasphase molecules cannot be explained uniquely by reactions taking place in the gas phase but
chemical reactions occurring on the surfaces of grains are essential to rationalize theinterstellar chemistry. However, combining astronomical observations with astrochemical
modelling and laboratory experiments is not enough to fully unveil the grain surface
chemistry and its contribution to the chemistry of space because they hold some intrinsic
limitations [4,5,6]. Quantum chemical simulations can partly alleviate this as they provide
reliable, quantitative atomic-scale information (structure, energetics, and dynamics) of
chemical processes taking place on the surface of grains, this way allowing us to determine
the actual role of the grains on them, that is, as chemical catalysts, reactant concentrator
and/or third bodies. This contribution aims to present some of the potentialities of current
state-of-the-art computations developed in the QuantumGrain group to obtain unique andfundamental information that help improving our know-how on the grain surface chemistry.
To this end, examples on the modelling of realistic grain surfaces for ices and silicates [7], on
simulations dealing with the adsorption of astrochemically-relevant species [8] and withchemical reactions forming ethanol from CCH reacting with water ice [9], and finally on thefate of the extra energy released in an exothermic reaction (here the H2 formation, [10]) will
be presented.

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