A computational study of CO 2 formation on interstellar H 2 O ice Harjasnoor Kakkar, Albert Rimola Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Catalonia, Spain Solid CO 2 has been detected in various physical environments in the interstellar medium (ISM) since its first observation in 1989. [1] Despite being one of the most abundant species in the ISM and a significant component of ice mantles on dust grains, the formation route of CO 2 remains uncertain. [2] The low abundance of CO 2 in the gas phase suggests that it is exclusively formed on the solid ice surface. Moreover, there is no clear, efficient process that can account for the majority of CO 2 formation. [3] In this study, we investigate three well-known radical-neutral reaction pathways (CO with O, CO with OH, and HCHO with O) on pure water ice clusters using quantum chemical calculations. Multiple density functional theory (DFT) functionals are employed to carry out the preliminary benchmarking study on the model gas-phase reactions and determine an accurate method for describing the reaction properties. With the selected functional, potential energy surfaces of the reactions are obtained on ice models i.e., two water clusters consisting of 18 and 33 molecules. First insights will be presented based on the computational investigation that aims to determine the energetically feasible reaction mechanisms. The astrophysical implications of the results will be discussed in combination with observations from experiments and astrochemical models of these widely studied reactions. References
1. J. E. Roser, G. Vidali, et al. Astrophys. J . 2001 , 555, L61-L64. 2. M. Minissale, E. Congiu, et al. Astron. Astrophys . 2013 , 559, A49. 3. R. T. Garrod, T. Pauly. Astrophys. J . 2011 , 735, 15.
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