Computational Framework For Analysis Of Hydrogen Bonding In The Oh Stretch Region

Dzugan, Laura C.

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https://hdl.handle.net/2142/50778 Copy

Description

Title

Computational Framework For Analysis Of Hydrogen Bonding In The Oh Stretch Region

Author(s)

Dzugan, Laura C.

Contributor(s)

McCoy, Anne B.

Issue Date

2014-06-19

Keyword(s)

Mini-symposium: Beyond the Mass-to-Charge Ratio: Spectroscopic Probes of the Structures of Ions

Abstract

There are two types of bands in the OH stretch region of the vibrational spectra of hydrogen-bonded complexes; narrow peaks due to isolated OH stretches and a broadened feature reflecting the OH stretches involved in strong hydrogen bonding. This second region can be as wide as several hundred wavenumbers and is shifted to the red of the narrow peaks. In this work we focus on (CaOH)$^{+}\cdot$(H$_{2}$O)$_n$ and (MgOH)$^{+}\cdot$(H$_{2}$O)$_{n}$ systems.$^{1}$ When n$<$4, the spectra are characterized by only the narrow peaks near 3700 cm$^{-1}$. When n$\ge$4, there is an additional band that is several hundred cm$^{-1}$ wide, which is attributed to hydrogen bonding. This breadth arises from coupling between the OH stretches in the water molecules and the low frequency modes of the complex. To understand the broadening observed in the spectra, we have developed a computational framework in which we sample displacement geometries from the equilibrium structure based on the ground state harmonic wavefunction. Then we combine the harmonic spectra in the OH stretch region for each computed geometry to generate the spectrum for this complex. As the calculated spectra agree well with the experimental spectra, we then investigated which geometric parameters in the system are correlated to the size of the red-shift of the frequencies. The hydrogen-bonded OH stretches were found to be very sensitive to how the water molecules were arranged around the hydroxide group. 1. Leavitt, C.M.; Johnson, C.J.; Johnson, M.A. Unpublished work.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

English

Permalink

http://hdl.handle.net/2142/50778

DOI

https://doi.org/10.15278/isms.2014.RG04

Copyright and License Information

Copyright 2014 by the authors. Licensed under a Creative Commons Attribution 4.0 International License. http://creativecommons.org/licenses/by/4.0/

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