Christie, Richard Andrew
(2005)
Theoretical studies of Hydrogen-bonded clusters.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Recent experimental findings and theoretical predictions have stimulatedconsiderable interest in the properties of Hydrogen-bonded clusters. Inthis dissertation, the water hexamer (H$_2$O)$_6$ and small protonatedwater clusters H$^+$(H$_2$O)$_n$ ($n=4,5,6,8,21$) are investigated bytheoretical means.H$^+$(H$_2$O)$_5$ is the smallest protonated water cluster with aH$_2$O molecule in the secondary solvation shell of H$^+$, and isinvestigated here with a variety of model potentials, density functionals andlarge basis set MP2 calculations. Upon inclusion of zero-point energy, theglobal minimum structure of H$^+$(H$_2$O)$_5$ can be considered as theEigen-cation with a H$_2$O H-bonded to a first-solvation shell molecule.Analysis of the harmonic vibrational spectra of energetically low-lyingH$^+$(H$_2$O)$_{4,5}$isomers reveals the spectroscopic signatures for the proton solvated in boththe Eigen and Zundel forms.The parallel tempering Monte Carlo method is used to explore theconfiguration space of H$^+$(H$_2$O)$_6$ and H$^+$(H$_2$O)$_8$ for thelowest-lying isomers, and to simulate the finite temperatureproperties of these clusters. A property of particular interest is thephase-change behavior of $n=6,8$. The dependence of theisomer populations of both $n=6$ and $8$ with temperature is found to be ingood agreement with the recent experimental findings of Jiang emph{et al.}@[emph{J.@ Am.@ Chem.@ Soc.@} extbf{2000}, emph{122}, 1398].The thermodynamic behavior of the (H$_2$O)$_6$ cluster has been the subject ofseveral theoretical studies employing model potentials. However, the resultsfrom these investigations vary considerably due to the different modelpotentials employed. New results are presented from studies employing anemph{ab initio} intermolecular potential. Canonical Monte Carlo simulationsusing a 2+3-body MP2-level potential are combined with finite histogram method ofFerrenberg and Swendsen [emph{Phys.@ Rev.@ Lett.@} extbf{1988}, emph{61}, 2635] tosimulate the finite temperature properties of (H$_2$O)$_6$.The emph{magic number} behavior of H$^+$(H$_2$O)$_{21}$ has stirred debatein the literature since the initial report by Searcy and Fenn[emph{J.@ Chem.@ Phys.@}, extbf{1974}, emph{61}, 5282].The OH stretching vibrational spectra for the $6le n le 27$ clustersare analyzed with the aid of MP2-level calculations, and a dodecahedral-basedconfiguration for $n=21$ is confirmed.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
|
| Date: |
31 January 2005 |
| Date Type: |
Completion |
| Defense Date: |
7 December 2004 |
| Approval Date: |
31 January 2005 |
| Submission Date: |
9 December 2004 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| 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: |
melatonin |
| Other ID: |
http://etd.library.pitt.edu/ETD/available/etd-12092004-154343/, etd-12092004-154343 |
| Date Deposited: |
10 Nov 2011 20:09 |
| Last Modified: |
15 Nov 2016 13:54 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/10238 |
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