China
Africa
Explore chapters and articles related to this topic
Structure Prediction from Scattering Profiles: A Neutron-Scattering Use-Case
Published in Anuj Karpatne, Ramakrishnan Kannan, Vipin Kumar, Knowledge-Guided Machine Learning, 2023
Cristina Garcia-Cardona, Ramakrishnan Kannan, Travis Johnston, Thomas Proffen, Sudip K. Seal
Crystallographic structure determination and refinement has been the cornerstone of materials science and our understanding of the atomic structure for many decades. The ability to design customized material with targeted mechanical and chemical properties relies on their internal structure. Neutron scattering is a state-of-the-art experimental technique that allows scientists to probe material structures with atomic resolutions by scattering beams of neutrons from them. While calculating the scattering intensities of a given crystal structure is straight forward, obtaining the atomic structure from the scattering intensities is not due to the so-called “crystallographic phase problem”. In a nutshell, the scattering intensities we measure only give us the amplitude of the structure factor F but not the phase value.
Epitaxial Silicene
Published in Klaus D. Sattler, 21st Century Nanoscience – A Handbook, 2020
Dmytro Solonenko, Patrick Vogt
The phonon frequencies (energies) can be probed by means of optical or electron spectroscopy. Two powerful spectroscopic methods are Raman spectroscopy, probing phonons at, and high-resolution electron energy loss spectroscopy (HREELS), probing phonons close to the zone edge and high-symmetry points. In order to map the phonon dispersions over the whole BZ, neutron scattering could be applied. Neutron scattering requires large bulk samples, a nuclear reactor as a neutron source, and a triple-axis spectrometer which make it an experimentally complicated technique. Raman spectroscopy, on the other hand, is relatively simple and a well-established non-destructive method to study 2D materials. Furthermore, Raman spectrometer can easily be attached to UHV preparation or analysis chambers and enables the in situ investigation of a 2D material without exposing it to air. As we have seen above, elemental 2D materials with low buckling are chemically reactive and would be modified or destroyed under ambient conditions by adsorption processes. Hence, in situ Raman spectra can be utilized as a fingerprint of a 2D material and allows, for example, its modification to be followed. Much more than this, the vibrational properties determined by Raman spectroscopy give deep insight into the structural, chemical, and electronic properties of the material.
Nuclear Particles, Processes, and Reactions
Published in Robert E. Masterson, Introduction to Nuclear Reactor Physics, 2017
Neutron scattering experiments can be used to understand the atomic structure of many solids and liquids. Neutron scattering experiments are used to determine the exact positions, motions, and magnetic moments of atoms by investigating how neutrons collide with them and then measuring the change in the kinetic energy and the momentum of particles going into and out of the reactions. Experimental data obtained from these scattering experiments can then be used to infer the internal structure of the atom or molecule that is being investigated.
Measurements of Neutron Scattering from a Copper Sample Using a Quasi-Differential Method in the Region from 2 keV to 20 MeV
Published in Nuclear Science and Engineering, 2022
E. Blain, Y. Danon, D. P. Barry, B. E. Epping, A. Youmans, M. J. Rapp, A. M. Daskalakis, R. C. Block
In an attempt to assist in determining which library is most accurate and provide data for future evaluations, the quasi-differential scattering method was developed at Rensselaer Polytechnic Institute4 (RPI). This method relies on performing a neutron scattering measurement and comparing it with detailed simulations of the experiment in order to determine which nuclear data library used in the simulations most accurately represents the experimental data. Additionally, the comparison can provide information in regions where none of the evaluations accurately model the data to identify areas that could be improved in future evaluations.