TY - GEN
T1 - Importance of Exchange Processes in Earth and Mars Atmospheric Kinetics
T2 - AIAA Science and Technology Forum and Exposition, AIAA SciTech Forum 2022
AU - Sharma, Maitreyee P.
AU - Venturi, Simone
AU - Jaffe, Richard L.
AU - Schwenke, David
AU - Panesi, Marco
N1 - The work was supported by NASA’s ESI grant no. 80NSSC19K0218 with Prof. Marco Panesi as the Principal Investigator. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of NASA or the U.S. government. The authors also acknowledge support from the NASA Space Technology Mission Directorate Entry Systems Modeling Project. Finally, the authors would like to thank Dr. Alessandro Munafo for providing the PLATO code used to study the isothermal bath simulations presented in this work.
The work was supported by NASA?s ESI grant no. 80NSSC19K0218 with Prof. Marco Panesi as the Principal Investigator. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of NASA or the U.S. government. The authors also acknowledge support from the NASA Space Technology Mission Directorate Entry Systems Modeling Project. Finally, the authors would like to thank Dr. Alessandro Munafo for providing the PLATO code used to study the isothermal bath simulations presented in this work.
PY - 2022
Y1 - 2022
N2 - HCN is an important molecule in interstellar chemistry, atmospheric reentry as well as combustion. This paper presents the construction of the ground state singlet HCN potential energy surface (PES),1 and state-to-state (StS) kinetics of the molecule-atom systems associated with HCN. The ground state HCN surface is associated to the ground state of CN (2 Σ+ ) and NH (3 Σ− ) and the first excited state of CH (4 Σ− ). Multi-reference configuration interaction calculations are used to compute the ab-initio points on a grid of geometries for the diatomic potentials and the full PES. A total of 11688 ab-initio points are used to construct the potential energy surface. The diatomic potentials are fit to the Modified Morse functional form and the potential energy surface fit is obtained using a permutationally invariant polynomial neural network (PIP-NN). The RMS error in the potential energy surface fit are is upto 0.2 eV in the 0-25 eV energy range. The PES constructed highlights some important topological features. Firstly, the exchange of CH and NH to CN is barrier-less and second, the potential energy surface is characterized by two deep wells corresponding to HCN and HNC molecules in their ground singlet states. The considerably larger depth of the CN molecule diatomic potential and the barrier-less exchange pathway make exchange reactions and exchange assisted dissociation important kinetic features of the system. The potential energy surface constructed is used to carry out quasi-classical trajectory calculations followed by state-to-state isothermal heat bath simulations to study macroscopic quantities of interest to atmospheric entry. Furthermore, the exchange associated dissociation in CH and NH causes the dissociation to happen an order of magnitude faster in time when compared to only direct dissociation with the contribution due to exchange being 84.7% and 82.5% in the dissociation source terms, respectively.
AB - HCN is an important molecule in interstellar chemistry, atmospheric reentry as well as combustion. This paper presents the construction of the ground state singlet HCN potential energy surface (PES),1 and state-to-state (StS) kinetics of the molecule-atom systems associated with HCN. The ground state HCN surface is associated to the ground state of CN (2 Σ+ ) and NH (3 Σ− ) and the first excited state of CH (4 Σ− ). Multi-reference configuration interaction calculations are used to compute the ab-initio points on a grid of geometries for the diatomic potentials and the full PES. A total of 11688 ab-initio points are used to construct the potential energy surface. The diatomic potentials are fit to the Modified Morse functional form and the potential energy surface fit is obtained using a permutationally invariant polynomial neural network (PIP-NN). The RMS error in the potential energy surface fit are is upto 0.2 eV in the 0-25 eV energy range. The PES constructed highlights some important topological features. Firstly, the exchange of CH and NH to CN is barrier-less and second, the potential energy surface is characterized by two deep wells corresponding to HCN and HNC molecules in their ground singlet states. The considerably larger depth of the CN molecule diatomic potential and the barrier-less exchange pathway make exchange reactions and exchange assisted dissociation important kinetic features of the system. The potential energy surface constructed is used to carry out quasi-classical trajectory calculations followed by state-to-state isothermal heat bath simulations to study macroscopic quantities of interest to atmospheric entry. Furthermore, the exchange associated dissociation in CH and NH causes the dissociation to happen an order of magnitude faster in time when compared to only direct dissociation with the contribution due to exchange being 84.7% and 82.5% in the dissociation source terms, respectively.
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U2 - 10.2514/6.2022-1013
DO - 10.2514/6.2022-1013
M3 - Conference contribution
AN - SCOPUS:85123431969
SN - 9781624106316
T3 - AIAA Science and Technology Forum and Exposition, AIAA SciTech Forum 2022
BT - AIAA SciTech Forum 2022
PB - American Institute of Aeronautics and Astronautics Inc, AIAA
Y2 - 3 January 2022 through 7 January 2022
ER -