Molecular Simulation of Xenon NMR in Fluids and Nanocavities

Thesis event information

Date and time of the thesis defence

Place of the thesis defence

Linnanmaa, lecture hall L5. Remote connection: https://oulu.zoom.us/j/64684269151

Topic of the dissertation

Molecular Simulation of Xenon NMR in Fluids and Nanocavities

Doctoral candidate

Master of Science Jouni Karjalainen

Faculty and unit

University of Oulu Graduate School, Faculty of Science, NMR Research Unit

Subject of study

Physics

Opponent

Professor emeritus Claudio Zannoni, University of Bologna

Custos

Docent Perttu Lantto, University of Oulu

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Simulated spectroscopy sheds light on the structure of fluids

The xenon nuclear magnetic resonance (NMR) parameters computed from molecular simulations confirmed the rich temperature-dependent phase structure of a liquid crystal confined to a nanosized cavity. The methods developed during the thesis work were also utilized in studying the still surprising properties of liquid water.

The computed spectral parameters validated the partially oriented phase previously found with experimental methods in liquid crystals confined to cylindrically-shaped nanocavities. The computed parameters were found to correspond qualitatively to previous experiments and give new interpretations to support experimental data. The methods developed during this research enabled separating factors contributing to the temperature dependence of NMR spectra of noble gases dissolved in liquids.

The study made extensive use of quantum-mechanically parameterised, simplified molecular models. These were used to describe both the electric interactions that govern the behaviour of the material in the simulation, as well as to compute the NMR chemical shift of dissolved xenon atoms. The combination of methods enabled efficient simulations of classical mechanics, as well as the direct comparison of simulation results to the experimental NMR spectra. The molecular simulations were run in the CSC supercomputing environment.

Liquid crystals are phases of matter, which have properties of both crystalline solids and liquids. When the liquid crystal substance is enclosed in a porous material, its rich phase behaviour can be further extended. The most well-known applications of liquid crystals in confined spaces are the liquid-crystal displays (LCDs) and the so-called smart windows.

Xenon NMR spectroscopy is a well-known tool of research for liquids, liquid crystals and porous materials. The NMR Research Unit in the University of Oulu has decades of experience in studying fluids, porous materials and nanosystems using both computational and experimental methods.
Last updated: 11.5.2021