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Carbon Monoxide Hydrogenation on Ice Surfaces
Author(s) -
Kuwahata Kazuaki,
Ohno Kaoru
Publication year - 2018
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201701346
Subject(s) - carbon monoxide , oniom , chemistry , interstellar ice , molecule , activation energy , amorphous ice , chemical physics , astrochemistry , amorphous solid , interstellar cloud , excitation , chemical reaction , density functional theory , computational chemistry , catalysis , interstellar medium , physics , crystallography , organic chemistry , quantum mechanics , galaxy
We have performed density functional calculations to investigate the carbon monoxide hydrogenation reaction (H+CO→HCO), which is important in interstellar clouds. We found that the activation energy of the reaction on amorphous ice is lower than that on crystalline ice. In the course of this study, we demonstrated that it is roughly possible to use the excitation energy of the reactant molecule (CO) in place of the activation energy. This relationship holds also for small water clusters at the CCSD level of calculation and the two‐layer‐level ONIOM (CCSD : X3LYP) calculation. Generally, since it is computationally demanding to estimate activation energies of chemical reactions in a circumstance of many water molecules, this relationship enables one to determine the activation energy of this reaction on ice surfaces from the knowledge of the excitation energy of CO only. Incorporating quantum‐tunneling effects, we discuss the reaction rate on ice surfaces. Our estimate that the reaction rate on amorphous ice is almost twice as large as that on crystalline ice is qualitatively consistent with the experimental evidence reported by Hidaka et al. [ Chem. Phys. Lett ., 2008, 456 , 36.]