relation: http://d-scholarship-dev.library.pitt.edu/7663/
title: VIBRATIONAL SPECTRA AND n-BODY DECOMPOSITION ANALYSESOF WATER CLUSTERS
creator: Cui, Jun
description: The hydrated proton lies at the heart of several key charge transport processes in chemistry and biology, and yet the molecular level description of proton accommodation remains elusive. Both H3O+ (so called Eigen) and (H2O···H···OH2)+ (so called Zundel) have long been thought to play essential roles in the proton transfer process. We characterize the hydrated proton with a "bottom up" approach to monitor the spectral evolution of the proton accommodation motif as water molecules are sequentially added to the H3O+ ion. It is found that a highly symmetrical structure is necessary to observe the Eigen ion. Small asymmetries in the hydration structure around the H3O+ core result in preferential localization of the excess charge on one or two of the hydrogen atoms. This extreme response to symmetry breaking readily explains the lack of a crisp spectral signature of the hydrated proton in the bulk. Density functional theory is used to study the relative stability of various isomers of (H2O)n · H+, n = 4-12, allowing for the influence of vibrational zero point energy and finite temperature effects. Comparison of experimental spectra with and without Ar tagging shows that the inclusion of Ar atoms has little effect on the frequencies.Two low-energy minima of (H2O)21 with very different H-bonding arrangements have been investigated with the B3LYP density functional and RIMP2 methods, as well as with the TIP4P, Dang-Chang, AMOEBA, and TTM2-F force fields. Insight into the role of many-body polarization for establishing the relative stability of the two isomers is provided by an n-body decomposition of the energies calculated using the various theoretical methods.
date: 2007-06-20
type: University of Pittsburgh ETD
type: PeerReviewed
format: application/pdf
language: en
identifier: http://d-scholarship-dev.library.pitt.edu/7663/1/cui_etd2007.pdf
identifier:   Cui, Jun  (2007) VIBRATIONAL SPECTRA AND n-BODY DECOMPOSITION ANALYSESOF WATER CLUSTERS.  Doctoral Dissertation, University of Pittsburgh.    (Unpublished)