Henderson, Elva
(2022)
Theoretical Techniques for the Study of Bonding, Vibrations, and Structures of Water-Ion Clusters.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
For decades, experimentalists and theoreticians have used gas-phase water-ion clusters to probe solute-solvent interactions at a molecular level. Vibrational spectroscopy on these clusters has yielded a wealth of information of the structure and dynamics of these small systems. This information can then be used to gain insight into the solvation interactions in a bulk system. However, despite their small size, these clusters are surprisingly complex, and much is still to be learned about these systems.
This work explores two contrasting approaches to the computational study of water-ion clusters. The first approach is the use of experimental references to build upon and expand theoretical techniques. The property of interest is vibrational progressions in the OH stretching regions of water-anion clusters of the form X– · (H2O) (where X– is a polyatomic anion). This progression arises from a coupling of the high-frequency OH stretching modes with low-frequency intermolecular rock modes. Although previous theoretical models have been able to qualitatively reproduce these progressions, obtaining quantitative agreement with experiment has proven more difficult. To tackle this problem, a one-dimensional adiabatic model was developed to directly model the effect of OH stretch excitation on the rocking mode. This model was further expanded into a two-dimensional model to reproduce these progressions with even greater accuracy.
The second approach is the use of computational techniques to aid in the interpretation and understanding of new experimental results on protonated water clusters. Experiments were performed by the Johnson group to observe the migration of a hydrogen atom over time in the D3O+ · (HDO)(D2O)19 cluster. These experiments showed that when the HOD monomer had a free OD stretch, the cluster could undergo an interconversion to yield a free OH stretch. A mix of computational techniques was used to confidently determine the pathway of this interconversion, in which the cluster goes through an intermediate state containing a four-membered ring
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
|
| Date: |
11 October 2022 |
| Date Type: |
Publication |
| Defense Date: |
21 July 2022 |
| Approval Date: |
11 October 2022 |
| Submission Date: |
5 August 2022 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
92 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Dietrich School of Arts and Sciences > Chemistry |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
Quantum chemistry, molecular vibrations, computational modeling, infrared spectroscopy, adiabatic model, DVR |
| Date Deposited: |
11 Oct 2022 19:55 |
| Last Modified: |
11 Oct 2022 19:55 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/43523 |
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