Dissertation
EFFECTS OF HYDROGEN-BONDING IN HYDROGEN-RICH MIXTURES UNDER PRESSURE: A SYSTEMATIC STUDY OF THE DEUTERIUM-WATER, DEUTERIUM-AMMONIA, AND DEUTERIUM-METHANE MIXTURES
Doctor of Philosophy (PhD), Washington State University
01/2014
Handle:
https://hdl.handle.net/2376/5096
Abstract
We have investigated the D2-H2O, D2-NH3, and D2-CH4 mixtures under pressure using confocal micro-Raman spectroscopy. The D2-H2O mixture was studied to 64 GPa. The spectral data indicate the presence of deuterated isotopes of water and hydrogen due to proton exchange reactions, which were observed over a wide pressure range. The Raman spectra show significant differences between the mixture and pure hydrogen or water samples. The hydrogen vibrational modes shift to higher frequencies without a frequency turnover and split into two bands, with each band containing additional modes. These changes suggest that the proton-ordering transition in the ice lattice occurs over a large pressure range between 28 and 50 GPa, which is lower than that of pure ice (40-80 GPa). All these changes indicate the presence of high internal pressure due to the repulsive interactions.
The D2-NH3 mixture was investigated to 50 GPa. The spectral data indicate that proton exchange reactions also occur in the D2-NH3 mixture, producing deuterated isotopes of hydrogen and ammonia. An assignment is given for the vibrational stretching modes of NH2D and NHD2. The vibrational modes of hydrogen isotopes in D2-NH3 are blue shifted with respect to those of the pure hydrogen isotopes and they exhibit asymmetries and splittings beginning at ~10 GPa. Similarly, the stretching vibrational modes indicate less attractive interactions in the mixtures relative to pure ammonia. This suggests the presence of repulsion and internal pressure in the D2-NH3 mixture.
Finally, the D2-CH4 mixture was investigated to 30 GPa. Somewhat surprisingly, proton exchange processes in the D2-CH4 mixture are highly limited, with no evidence of deuterated methane or hydrogen. The vibrational modes of D2-CH4 show overall agreement with those in pure D2 and CH4.
The bond length of the hydrogen molecules was calculated for the three mixtures using the spectral data. The above results suggest that the strength of repulsive interaction or the magnitude of internal pressure in the mixtures is proportional to the strength of hydrogen bonding in H2O, NH3, and CH4 in decreasing order. Hence, we suggest that the proton exchange is assisted by hydrogen bonding in these molecules.
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Details
- Title
- EFFECTS OF HYDROGEN-BONDING IN HYDROGEN-RICH MIXTURES UNDER PRESSURE
- Creators
- Gustav Michael Borstad
- Contributors
- Choong-Shik Yoo (Advisor)Christian Mailhiot (Committee Member)Gary S. Collins (Committee Member)Matthew D. McCluskey (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Physics and Astronomy, Department of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 166
- Identifiers
- 99900581645801842
- Language
- English
- Resource Type
- Dissertation