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A necessary criterion for obtaining accurate lattice parameters by Rietveld method
Masami Tsubota1, Jiro Kitagawa2
1Physonit Inc., 6-10 Minami-horikawa, Kaita, Aki, Hiroshima, 736-0044, Japan. tsubota@physonit.jp.
Scientific Reports
|November 15, 2017
Summary
Accurate lattice parameters require reproducible peak-shift data in Rietveld refinement. This study introduces a new criterion to improve accuracy by distinguishing experimental from analytical peak-shifts, enhancing crystallographic analysis.
Area of Science:
- Crystallography
- Materials Science
- Computational Chemistry
Background:
- The Rietveld method is a standard technique for crystal structure refinement.
- Accurate determination of lattice parameters is crucial for understanding material properties.
- The conventional Rietveld method may yield homothetic, rather than true, unit cells.
Purpose of the Study:
- To investigate the relationship between lattice parameters and peak-shift in Rietveld refinement.
- To identify sources of error in peak-shift measurements.
- To propose an improved criterion for accurate lattice parameter determination.
Main Methods:
- Analysis of peak-shift, defined as the deviation from theoretical Bragg positions.
- Distinguishing between experimental and analytical peak-shifts.
- Development of a novel criterion based on peak-shift reproducibility.
Main Results:
- Fitting accuracy of lattice parameters is directly correlated with peak-shift reproducibility.
- Analytical peak-shift can erroneously reduce the reliability factor (Rwp).
- The proposed criterion demonstrates good reproducibility of experimental peak-shift.
Conclusions:
- The conventional Rietveld method's reliance on Rwp can be misleading.
- An additional criterion based on peak-shift is proposed for enhanced accuracy.
- The new method significantly improves the accuracy of determined lattice parameters.
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