Model-independent structure factors from powder X-ray diffraction: a novel approach

Area of Science:

• Materials Science
• Crystallography
• X-ray Diffraction

Background:

• Powder X-ray diffraction (PXRD) is crucial for determining crystal structures.
• Accurate determination of Bragg intensities is essential for structural analysis.
• Traditional PXRD methods often require complex parameter fitting.

Purpose of the Study:

• To present a simplified method for obtaining Bragg intensities from PXRD data.
• To demonstrate a condition where Bragg peak shapes are independent of scattering angle.
• To validate the method by deriving structure factors for diamond powder.

Main Methods:

• Utilizing a specific experimental setup at the P02.1 beamline at PETRA III.
• Employing a 60 keV X-ray beam from a 23 mm-period undulator.
• Ensuring consistent Bragg peak shapes by controlling sample holder (capillary) diameter and detector pixel size for 1 µm grain sizes.

Main Results:

• Achieved a condition where all Bragg peaks in a PXRD pattern exhibit the same shape.
• Demonstrated that peak shape is independent of scattering angle under these conditions.
• Derived structure factors for diamond powder that align with density functional theory calculations (WIEN2k).

Conclusions:

• The developed method allows for direct determination of Bragg intensities without fitting.
• This simplification facilitates accurate electron density analysis.
• The findings offer a more efficient approach to crystallographic studies using PXRD.