Anisotropy of extinction: extrapolation to the kinematical limit by γ-ray diffraction

Area of Science:

• Crystallography
• Materials Science
• Solid State Physics

Background:

• Anisotropic extinction poses challenges in accurately determining crystal structure factors.
• Existing models for extinction correction can be complex and require specific assumptions about crystal mosaicity.

Purpose of the Study:

• To present a direct experimental method for addressing anisotropic extinction.
• To validate Zachariasen's theory for high-energy X-ray diffraction.
• To determine kinematical structure-factor values without relying on anisotropic models.

Main Methods:

• Performed structure-factor measurements on vanadium and niobium crystals.
• Utilized four gamma-ray wavelengths (0.02-0.06 Å) for high-energy diffraction.
• Applied Zachariasen's theory to extrapolate diffraction data to zero extinction.

Main Results:

• Experimental data substantiated the applicability of Zachariasen's theory in high-energy diffraction.
• A method was developed to determine structure factors by fitting theoretical curves to experimental points.
• The approach successfully determined kinematical structure factors without assuming anisotropy models.

Conclusions:

• Zachariasen's theory is adequate for high-energy diffraction, simplifying extinction correction.
• The direct experimental approach provides a reliable method for determining crystal structure factors.
• This work offers a model-independent way to correct for anisotropic extinction in diffraction studies.