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Efficient and automated calculation schemes for chemical reaction rates
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Chantreau Majerus, Raphael (2022) Efficient and automated calculation schemes for chemical reaction rates. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b3913358~S15
Abstract
With the development of automated reaction discovery (ARD) methods as a tool to generate and describe chemical reaction networks, the need for rapid and accurate screening of either undesirable or unfeasible chemical reactions has become essential. Two common ways to screen through chemical reactions include using reaction rates, typically determined using transition state theory (TST), and characteristics of the minimum energy path such as energy barriers. Whilst TST is a popular method for determining reaction rates, the no recrossing assumption can lead to important differences in the dynamically correct reaction rate. As an alternative, the reaction path Hamiltonian (RPH) coupled to reactive flux dynamics has been shown to be able to account for recrossing occurring in the reaction, resulting in the dynamically correct reaction rate. However, the determination of the dynamically correct reaction using the RPH comes at a significant computational cost which makes this method unfeasible in the context of ARD. As such, in this work, a novel way to reduce the computational cost associated with constructing the RPH by implementing update Hessian schemes is used. The advantage of using update Hessian schemes to construct the RPH lies within the significant reduction Hessian evaluations, which are essential to the RPH. Results for this implementation were very positive, where a significant improvement on the computational cost was demonstrated, while keeping a similar level of accuracy depending on which update Hessian scheme was used. In addition to this work, the RPH is used to investigate dynamical effects in the Heck–Breslow mechanism for alkene hydroformylation with a cobalt catalyst, both in gas-phase and in solvent-phase. Moreover, the RPH reaction rates were compared to the TST reaction rates in the determination of the rate law to assess the importance of accounting for recrossing effects. Our results showed evidence of recrossing in the catalytic cycle, however, the kinetic simulations and the rate law showed little to no difference between TST and RPH reaction rates. Finally, as a way of improving on initial paths for nudged elastic band to determine minimum energy paths, we present two novel methods which use a navigation function as a driving force to determine a reaction path. The two novel methods are compared to other popular methods with the same goal and their performance is assessed in the context of computational cost required and overall accuracy.
Item Type: | Thesis (PhD) | ||||
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Subjects: | Q Science > QD Chemistry | ||||
Library of Congress Subject Headings (LCSH): | Chemical reactions -- Data processing, Chemical reactions -- Mathematical models | ||||
Official Date: | September 2022 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | Department of Chemistry | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Habershon, Scott | ||||
Sponsors: | University of Warwick. Molecular Analytical Science Centre for Doctoral Training ; Engineering and Physical Sciences Research Council | ||||
Format of File: | |||||
Extent: | 190 pages : illustrations (some colour) | ||||
Language: | eng |
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