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DOE OSTI · 1031003

Oxygen as a site specific structural probe in neutron diffraction

Neuefeind, Joerg C·Salmon, Phil·Zeidler, Anita·Fischer, Henry E·Rauch, Helmut·ten·Markland, Thomas·Lemmel, Hartmut
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Abstract

Oxygen is a ubiquitous element, playing an essential role in most scientific and technological disciplines, and is often incorporated within a structurally disordered material where examples include molten silicates in planetary science, glasses used for lasers and optical communication, and water in biological processes. Establishing the structure of a liquid or glassy oxide and thereby its relation to the functional properties of a material is not, however, a trivial task owing to the complexity associated with atomic disorder. Here we approach this challenge by measuring the bound coherent neutron scattering lengths of the oxygen isotopes with the sensitive technique of neutron interferometry. We find that there is a small but finite contrast of 0.204(6) fm between the scattering lengths of the isotope 18O and oxygen of natural isotopic abundance natO, contrary to tables of recommended values. This has enabled us to investigate the structure of both light and heavy water by exploiting, for the first time, the method of oxygen isotope substitution in neutron diffraction, thus circumventing many of the significant problems associated with more traditional methods in which hydrogen is substituted by deuterium. We find a difference of ~0.5% between the O-H and O-D intra-molecular bond distances which is much smaller than recent estimates based on diffraction data and is found to be in excellent agreement with path integral molecular dynamics simulations made with a flexible polarisable water model. Our results demonstrate the potential for using oxygen isotope substitution as a powerful and effective site specific probe in a plethora of materials, of pertinence as instrumentation at next generation neutron sources comes online

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08 HYDROGENABUNDANCEDEUTERIUMDIFFRACTIONFUNCTIONALSHEAVY WATERHYDROGENINTERFEROMETRYLASERSNATONEUTRON DIFFRACTIONNEUTRON SOURCESNEUTRONSOXIDESOXYGENOXYGEN ISOTOPESPATH INTEGRALSPROBESSCATTERING LENGTHSSILICATESWATER

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Neuefeind, Joerg C, Salmon, Phil, Zeidler, Anita, Fischer, Henry E, Rauch, Helmut, ten, Markland, Thomas, Lemmel, Hartmut. 2011-01-01. Oxygen as a site specific structural probe in neutron diffraction. https://www.osti.gov/biblio/1031003

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