Reactivity of the O2+.(H2O)n and NO+.(H2O)n cluster ions in the D-region of the ionosphere
The structure, spectroscopy and reactivity of hydrated dioxygenyl cluster ions O2+.(H2O)n with n = 1 – 5 has been theoretically investigated for the first time to understand potential reaction pathways that may convert O2+, present in high abundance in the upper layers of the ionosphere (E-region),...
| Main Author: | |
|---|---|
| Format: | Thesis (University of Nottingham only) |
| Language: | English |
| Published: |
2018
|
| Subjects: | |
| Online Access: | https://eprints.nottingham.ac.uk/55573/ |
| _version_ | 1848799186706759680 |
|---|---|
| author | Sharma, Sainish |
| author_facet | Sharma, Sainish |
| author_sort | Sharma, Sainish |
| building | Nottingham Research Data Repository |
| collection | Online Access |
| description | The structure, spectroscopy and reactivity of hydrated dioxygenyl cluster ions O2+.(H2O)n with n = 1 – 5 has been theoretically investigated for the first time to understand potential reaction pathways that may convert O2+, present in high abundance in the upper layers of the ionosphere (E-region), into protonated water clusters, which are the predominant positively charged ion species in the lower D-region. The reactivity of hydrated nitrosonium as NO+.(H2O)n with n = 4 – 5 has also been reinvestigated to clarify the potential intramolecular reaction for the formation of nitrous acid and a protonated water cluster.
Lowest energy geometries, binding energies and harmonic vibrational frequencies have been obtained for O2+.(H2O)n (n = 1 – 5) cluster ions. Through performing geometry optimisation calculations on O2+.(H2O) using coupled cluster theory (CCSD(T)), second order Møller-Plesset perturbation theory (MP2) and density functional theory (DFT) with a wide range of exchange-correlation functionals, it was found that the MP2/6-311++G** level of theory was reliable for the calculation of minimum energy geometries and harmonic vibrational frequencies. In particular, methods that include 100% exact Hartree-Fock exchange such as MP2 and M06-HF were found to accurately describe the charge distribution in the clusters. MP2-based Born-Oppenheimer ab initio molecular dynamics (AIMD) simulations of the reactions of the O2+.(H2O)n and NO+.(H2O)n cluster ions to form protonated water clusters reveal different mechanisms for the O2+ and NO+ based ions. AIMD simulations of O2+.(H2O)n (n = 2 – 5) with initial velocities of the atoms sampled from the Maxwell-Boltzmann distribution at 220 K show that following charge transfer, a reaction to form a protonated water cluster and OH radical occurs rapidly where the neutral O2 molecule is just a spectator. In contrast, the reaction of NO+.(H2O)n (n = 4 – 5) has been hypothesised to involve an intracluster reaction, but no reaction is observed in the AIMD simulations using thermal initial velocities. AIMD simulations of a water molecule colliding with NO+.(H2O)4 to form NO+.(H2O)5 were performed to establish whether the resulting activated complex, with excess energy, would be more susceptible to forming a protonated water cluster and nitrous acid. The simulations showed that an intramolecular reaction could occur and was dependant on the impact direction and velocity of the incoming water molecule. |
| first_indexed | 2025-11-14T20:31:40Z |
| format | Thesis (University of Nottingham only) |
| id | nottingham-55573 |
| institution | University of Nottingham Malaysia Campus |
| institution_category | Local University |
| language | English |
| last_indexed | 2025-11-14T20:31:40Z |
| publishDate | 2018 |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | nottingham-555732025-02-28T14:18:28Z https://eprints.nottingham.ac.uk/55573/ Reactivity of the O2+.(H2O)n and NO+.(H2O)n cluster ions in the D-region of the ionosphere Sharma, Sainish The structure, spectroscopy and reactivity of hydrated dioxygenyl cluster ions O2+.(H2O)n with n = 1 – 5 has been theoretically investigated for the first time to understand potential reaction pathways that may convert O2+, present in high abundance in the upper layers of the ionosphere (E-region), into protonated water clusters, which are the predominant positively charged ion species in the lower D-region. The reactivity of hydrated nitrosonium as NO+.(H2O)n with n = 4 – 5 has also been reinvestigated to clarify the potential intramolecular reaction for the formation of nitrous acid and a protonated water cluster. Lowest energy geometries, binding energies and harmonic vibrational frequencies have been obtained for O2+.(H2O)n (n = 1 – 5) cluster ions. Through performing geometry optimisation calculations on O2+.(H2O) using coupled cluster theory (CCSD(T)), second order Møller-Plesset perturbation theory (MP2) and density functional theory (DFT) with a wide range of exchange-correlation functionals, it was found that the MP2/6-311++G** level of theory was reliable for the calculation of minimum energy geometries and harmonic vibrational frequencies. In particular, methods that include 100% exact Hartree-Fock exchange such as MP2 and M06-HF were found to accurately describe the charge distribution in the clusters. MP2-based Born-Oppenheimer ab initio molecular dynamics (AIMD) simulations of the reactions of the O2+.(H2O)n and NO+.(H2O)n cluster ions to form protonated water clusters reveal different mechanisms for the O2+ and NO+ based ions. AIMD simulations of O2+.(H2O)n (n = 2 – 5) with initial velocities of the atoms sampled from the Maxwell-Boltzmann distribution at 220 K show that following charge transfer, a reaction to form a protonated water cluster and OH radical occurs rapidly where the neutral O2 molecule is just a spectator. In contrast, the reaction of NO+.(H2O)n (n = 4 – 5) has been hypothesised to involve an intracluster reaction, but no reaction is observed in the AIMD simulations using thermal initial velocities. AIMD simulations of a water molecule colliding with NO+.(H2O)4 to form NO+.(H2O)5 were performed to establish whether the resulting activated complex, with excess energy, would be more susceptible to forming a protonated water cluster and nitrous acid. The simulations showed that an intramolecular reaction could occur and was dependant on the impact direction and velocity of the incoming water molecule. 2018-12-11 Thesis (University of Nottingham only) NonPeerReviewed application/pdf en arr https://eprints.nottingham.ac.uk/55573/1/Thesis.pdf Sharma, Sainish (2018) Reactivity of the O2+.(H2O)n and NO+.(H2O)n cluster ions in the D-region of the ionosphere. MSc(Res) thesis, University of Nottingham. Quantum Chemistry Atmospheric Chemistry Theoretical Chemistry; Ionosphere |
| spellingShingle | Quantum Chemistry Atmospheric Chemistry Theoretical Chemistry; Ionosphere Sharma, Sainish Reactivity of the O2+.(H2O)n and NO+.(H2O)n cluster ions in the D-region of the ionosphere |
| title | Reactivity of the O2+.(H2O)n and NO+.(H2O)n cluster ions in the D-region of the ionosphere |
| title_full | Reactivity of the O2+.(H2O)n and NO+.(H2O)n cluster ions in the D-region of the ionosphere |
| title_fullStr | Reactivity of the O2+.(H2O)n and NO+.(H2O)n cluster ions in the D-region of the ionosphere |
| title_full_unstemmed | Reactivity of the O2+.(H2O)n and NO+.(H2O)n cluster ions in the D-region of the ionosphere |
| title_short | Reactivity of the O2+.(H2O)n and NO+.(H2O)n cluster ions in the D-region of the ionosphere |
| title_sort | reactivity of the o2+.(h2o)n and no+.(h2o)n cluster ions in the d-region of the ionosphere |
| topic | Quantum Chemistry Atmospheric Chemistry Theoretical Chemistry; Ionosphere |
| url | https://eprints.nottingham.ac.uk/55573/ |