CRAHCN-O: A Consistent Reduced Atmospheric Hybrid Chemical Network Oxygen Extension for Hydrogen Cyanide and Formaldehyde Chemistry in CO2-, N2-, H2O-, CH4-, and H2-Dominated Atmospheres

Abstract

Hydrogen cyanide (HCN) and formaldehyde (H2CO) are key precursors to biomolecules such as nucleobases and amino acids in planetary atmospheres; However, many reactions which produce and destroy these species in atmospheres containing CO2 and H2O are still missing from the literature. We use a quantum chemistry approach to find these missing reactions and calculate their rate coefficients using canonical variational transition state theory and Rice-Ramsperger-Kassel-Marcus/master equation theory at the BHandHLYP/aug-cc-pVDZ level of theory. We calculate the rate coefficients for 126 total reactions, and validate our calculations by comparing with experimental data in the 39% of available cases. Our calculated rate coefficients are most frequently within an factor of 2 of experimental values, and generally always within an order of magnitude of these values. We discover 45 previously unknown reactions, and identify 6 from this list that are most likely to dominate H2CO and HCN production and destruction in planetary atmospheres. We highlight ${}^1$O + CH3 $\to$ H2CO + H as a new key source, and H2CO + ${}^1$O $\to$ HCO + OH as a new key sink, for H2CO in upper planetary atmospheres. In this effort, we develop an oxygen extension to our consistent reduced atmospheric hybrid chemical network (CRAHCN-O), building off our previously developed network for HCN production in N2-, CH4-, and H2-dominated atmospheres (CRAHCN). This extension can be used to simulate both HCN and H2CO production in atmospheres dominated by any of CO2, N2, H2O, CH4, and H2.

Accepted for publication in J Phys Chem A, 21 pages, 4 tables, 35 supplementary pages

References in corpus (3)

• Atom-Tunneling in Chemistry
• A Consistent Reduced Network for HCN Chemistry in Early Earth and Titan Atmospheres: Quantum Calculations of Reaction Rate Coefficients
• HCN production in Titan's Atmosphere: Coupling quantum chemistry and disequilibrium atmospheric modeling

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• An experimental and theoretical investigation of HCN production in the Hadean Earth atmosphere
• Deep Mantle-Atmosphere Coupling and Carbonaceous Bombardment: Options for Biomolecule Formation on an Oxidized Early Earth
• Hydrocarbon complexity and photochemical shielding of prebiotic feedstock molecules in exoplanet atmospheres