Thermal neutron scattering cross sections of beryllium and magnesium oxides

Al-Qasir, I. I.; Jisrawi, N.; Gillette, V.H.; Qteish, A.

doi:10.1016/j.anucene.2015.09.006

Cited by 10 publications

(6 citation statements)

References 32 publications

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“…In this subsection, we report the neutron filter efficiencies of MgF 2 and BeF 2 as functions of the incident neutron energy, at T = 20, 40, 77, 200 and 293 K. These results will be discussed together with those of MgO and BeO. Note that the filter efficiencies of the last two compounds have recently been investigated (Al-Qasir et al, 2016) down to 77 K. Here, they are calculated at the above four considered temperatures. The obtained results for these four compounds are shown in Fig.…”

Section: Filter Efficiencymentioning

confidence: 98%

“…For MgF 2 , the results are discussed in comparison with the available experimental data as well as with those obtained by using the semi-empirical model (Freund, 1983;Steyerl, 1977). The calculated absorption and inelastic neutron scattering cross sections are used, in turn, to investigate the neutron filter efficiency of MgF 2 and BeF 2 and the neutron transmission through them (Al-Qasir et al, 2016). The obtained filter efficiencies are discussed in comparison with those of MgO and BeO (Al-Qasir et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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Neutron filter efficiency of beryllium and magnesium fluorides

Al-Qasir

Qteish

2017

J Appl Cryst

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The neutron filter efficiency of MgF2 and BeF2 has been investigated as a function of neutron incident energy at different temperatures, starting from the phonon density of states (PDOS) calculated using first‐principles techniques, and the results are compared with those of MgO and BeO. Recently, MgF2 has been suggested as a neutron filter and neutron transmission through it has been experimentally studied. For MgF2, excellent agreement between calculated and available experimental data has been achieved for the phonon dispersion relations, constant‐volume specific heat, inelastic scattering cross sections and neutron transmission. The PDOSs of MgF2 and BeF2 are found to differ significantly owing to the crystal structure and the cations' mass difference. The inelastic scattering cross sections and filter efficiencies of MgF2 and BeF2 show different behaviours, which can be understood to originate from the above PDOS incongruity and the large difference in absorption cross sections of Be and Mg nuclei. BeF2 is predicted to be a better neutron filter than MgF2 and MgO, over the temperature range of interest, while it has less ability than BeO to transmit low‐energy neutrons.

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Section: Filter Efficiencymentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Neutron filter efficiency of beryllium and magnesium fluorides

Al-Qasir

Qteish

2017

J Appl Cryst

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“…The B 1g and E 2g belong to longitudinal and transverse optical modes, respectively, and only doubly degenerate E 2g mode is Raman-active. However, several other phonon bands may also be excited, which is originated by phonon density of state (PDOS) and defects. − The Be is a semimetal, which has shown a large electron–phonon coupling effect at the Be(0001) surface . This coupling may induce a possible effect on phonon excitation using Raman scattering.…”

Section: Introductionmentioning

confidence: 99%

Microstructural Transformation of Nanoscale Be Layers in the Mo/Be and Be/Mo Periodic Multilayer Mirrors Investigated by Raman Spectroscopy

et al. 2021

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Raman scattering studies were carried out for the investigation of bonding and microstructural properties of dimensionally confined nanoscale Be layers in the periodic Mo/Be and Be/Mo multilayer structures. The amorphous phase of alternate periodic Be nanolayers was partially transformed into the crystalline phase at the critical thickness of 2.44 nm. Crystallinity was further improved with the increase in the thickness of the periodic Be layers, which was associated with the decline of the surface-to-volume ratio of Be–Be bonding. However, upon thermal annealing, the bond-order defects in the crystalline Be phase gradually increased due to thermal stretching of Be–Be bonding. Beyond the critical annealing temperature of 573 K, a complete transformation of crystalline to ultrashort-ranged amorphous Be phase was observed in the multilayer structures. At critical thicknesses, the transformation of amorphous Mo and Be nanolayers into the polycrystalline structure was confirmed by the combination of X-ray diffraction and Raman scattering studies, respectively.

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“…There is thus a great incentive for its calculation and prediction from theory, with little or no experimental input other than the tabulated cross-section for each constituent element/isotope . With the development of computing power, such calculations have evolved from the early-stage analytical/synthetic models to the more recent efforts based on density functional theory (DFT), including methods using ab initio lattice dynamics − and molecular dynamics. , The LEAPR and THERMR modules of NJOY code are widely used for the elastic and inelastic neutron scattering cross-section calculations, starting from the phonon density of states. However, there are several approximations and limitations involved in the NJOY approach, including the incoherent approximation (also used in the Monte Carlo-based thermal neutron transport library NCrystal), cubic approximation, as well as limitations on the structure and composition of the material. , The importance of the coherent effects was recognized early via studying strong coherent scatterers such as beryllium and graphite. − Recently, the effects of coherent inelastic scattering have been studied by introducing a correction of one-phonon scattering into the NJOY workflow. ,, Moreover, the newly developed Full Law Analysis Scattering System Hub (FLASSH) represents the most up-to-date advance in removing the approximations and addressing the limitations associated with the NJOY code.…”

Section: Introductionmentioning

confidence: 99%

Calculation of the Thermal Neutron Scattering Cross-Section of Solids Using OCLIMAX

Cheng

Ramirez‐Cuesta

2020

J. Chem. Theory Comput.

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The thermal neutron scattering cross-section of a solid depends on the energy (or wavelength) of the incident neutrons. Devising a method to calculate the energy dependence from first principles, without the approximations built in the scattering theory, has been a major undertaking in nuclear engineering. Here, we demonstrate such a calculation method using the program OCLIMAX. Our approach eliminates various approximations and limitations involved in a regular calculation with the LEAPR module of NJOY code, and the results are compared with available experimental and theoretical data. It is also demonstrated how additional insight can be obtained from the calculated full dynamical structure factor. The results reported here show the great potential and excellent platform provided by OCLIMAX for future development in the study of neutron thermalization in solid materials for different applications.

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Thermal neutron scattering cross sections of beryllium and magnesium oxides

Cited by 10 publications

References 32 publications

Neutron filter efficiency of beryllium and magnesium fluorides

Neutron filter efficiency of beryllium and magnesium fluorides

Microstructural Transformation of Nanoscale Be Layers in the Mo/Be and Be/Mo Periodic Multilayer Mirrors Investigated by Raman Spectroscopy

Calculation of the Thermal Neutron Scattering Cross-Section of Solids Using OCLIMAX

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