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Persistent URL http://purl.org/net/epubs/work/57832285
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Title Inelastic neutron scattering study of thymol and para-cymene as potential neutron moderating materials.
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Abstract Neutron moderators can have many forms and sizes with water (H2O), methane (CH4) and molecular hydrogen (H2) being the most commonly used moderating materials. These materials have very good neutron moderating characteristics, such as high proton density leading to favorable energy distributions of moderated neutrons, but they can have serious disadvantages as well. Solid methane is prone to radiolysis resulting in a variety of recombinant species, as well as gaseous hydrogen, which can damage the containing vessel. The H2 moderator is currently only feasibly contained in liquid form at spallation type sources which ultimately leads to a broadened energy distribution of the moderated neutrons. As a result, the active search for new types of moderator materials, and especially cryogenic moderator materials, is underway around the world. This has led to the investigation of thymol (C10H14O), as well as para-cymene (C10H14), both hydrogen rich compounds. To better describe these hydrogenous molecules, inelastic neutron scattering (INS), infrared and Raman spectra of thymol, as well as para-cymene were collected. The experimental data were then compared with theoretically derived vibrational frequencies calculated for the single molecule optimised geometries at the B3LYP/6-311++G(d,p) level of theory using Gaussian 16. Finally, the AbINS software, as implemented in Mantid, was used to simulate the INS spectra from the vibrational frequencies and the mean squared displacements of atoms from their equilibrium position. From the obtained results it was shown that both thymol and para-cymene possessed favorable, low energy, vibrational modes involving the rotation of their benzene-bound methyl groups. These results suggested that both materials have favorable neutron moderating characteristics. As a conclusion it is emphasized that the glassy state of para-cymene should be analysed in more details.
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Language English (EN)
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Thesis MSc, University of Copenhagen, 2023. Zeppelin_2023_Cop…erator_materials.pdf 2023