Unraveling the Interface Chemistry between HCN and Cosmic Silicates by the Interplay of Infrared Spectroscopy and Quantum Chemical Modeling
Bancone, Niccolò (Universitat Autònoma de Barcelona. Departament de Química)
Santalucia, Rosangela (Università degli Studi di Torino)
Pantaleone, Stefano (Università degli Studi di Torino)
Ugliengo, Piero (Università degli Studi di Torino)
Mino, Lorenzo (Università degli Studi di Torino)
Rimola, Albert (Universitat Autònoma de Barcelona. Departament de Química)
Corno, Marta (Universitat Autònoma de Barcelona. Departament de Química)

Data:	2024
Resum:	Understanding the interaction between hydrogen cyanide (HCN) and silicate surfaces is crucial for elucidating the prebiotic processes occurring on interstellar grain cores as well as in cometary and meteoritic matrices. In this study, we characterized the adsorption features of HCN on crystalline forsterite (MgSiO) surfaces, one of the most abundant cosmic silicates, by combining experimental infrared spectra at low temperatures (100-150 K) with periodic DFT simulations. Results showed the coexistence of both molecular and dissociative HCN adsorption complexes as a function of the considered forsterite crystalline face. Molecular adsorptions dominate on the most stable surfaces, while dissociative adsorptions occur predominantly on surfaces of lower stability, catalyzed by the enhanced Lewis acid-base behavior of surface-exposed Mg-O ion pairs. On the whole set of adsorption cases, harmonic frequency calculations were carried out and compared with the experimental infrared bands. To disentangle each vibrational mode contributing to the experimental broad bands, we run the best nonlinear fit between the predicted set of frequencies and the experimental bands. The outcome of this procedure allowed us to (i) deconvolute the experimental IR spectrum by assigning computed normal modes of vibrations to the main features of each band and (ii) reveal which crystal faces are responsible for the largest contribution to the adsorbate vibrational bands, giving information about the morphology of the samples. The present straightforward procedure is quite general and of broad interest in the fine characterization of the infrared spectra of adsorbates on complex inorganic material surfaces.
Ajuts:	European Commission 865657 Agencia Estatal de Investigación CNS2023-144902 Agencia Estatal de Investigación PID2021-126427NB-I00
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Llengua:	Anglès
Document:	Article ; recerca ; Versió acceptada per publicar
Matèria:	Cosmic silicates ; Forsterites ; Hydrogen Cyanide ; Infrared spectrum ; Infrared: spectroscopy ; Interface chemistry ; Mg 2 ; Quantum-chemical model ; Silicate surfaces
Publicat a:	Journal of physical chemistry. C, Vol. 128, Issue 36 (September 2024) , p. 15171-15178, ISSN 1932-7455

DOI: 10.1021/acs.jpcc.4c03454

Postprint 23 p, 10.2 MB

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