Remarkable Precision of the 90-Year-Old Dynamical Diffraction Theories of Darwin and Ewald

Journal Article · Fri Jan 01 04:00:00 EST 2010 · Journal of Applied Crystallography

DOI:https://doi.org/10.1107/S0021889810021072· OSTI ID:1050250

Agamalian, Michael ^[1]; Carpenter, John M ^[1]

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1. ORNL

The reflectivity functions calculated by Bonse and Hart for a multi-bounce channel-cut single crystal following the 90-year-old Darwin and Ewald theories exhibit extremely narrow, nearly rectangular profiles. This feature provides ultra-high angular resolution and sensitivity for the double-crystal diffractometers now widely used for observation of large-scale structures in condensed matter. However, the experimental results are several orders of magnitude poorer than the theoretical prediction, the wings problem , and the reason for this discrepancy has remained unidentified for more than 40 years, creating problems for both theory and practice. Here we show a complete solution of this problem for neutron diffraction in Si channel-cut crystals. Our results allow obtaining nearly theoretical functions of multiple reflectivity, which demonstrates the remarkable precision of the Darwin and Ewald theories in the range of the wings and give rise to much improved sensitivity for the next generation of the Bonse-Hart double-crystal diffractometers.

• Research Organization: Oak Ridge National Laboratory (ORNL); Spallation Neutron Source
• Sponsoring Organization: SC USDOE - Office of Science (SC)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1050250
• Journal Information: Journal of Applied Crystallography, Journal Name: Journal of Applied Crystallography Journal Issue: 4 Vol. 43; ISSN JACGAR; ISSN 0021-8898
• Country of Publication: United States
• Language: English

Related Subjects

99 GENERAL AND MISCELLANEOUS
ACCURACY
DIFFRACTION
DIFFRACTOMETERS
FORECASTING
MONOCRYSTALS
NEUTRON DIFFRACTION
REFLECTIVITY
RESOLUTION
SENSITIVITY