CALCULATOR
PDF Q-range design
Check whether representative low-angle Bragg reflections are covered and estimate the PDF real-space resolution.
- Q range
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- Δr ≈ π / Qmax
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- Representative reflections covered
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| Reflection | d [Å] | Q [Å−1] | 2θ [°] | Status |
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How to use
Enter the lattice constant a, X-ray wavelength λ, and measured Q range. The default values assume ZIF-8 with a = 16.99 Å and a measurement using λ = 0.496054 Å. “Covered” means that the geometric reflection position lies between Qmin and Qmax.
For example, with Qmin = 0.70 Å−1, the ZIF-8 (110) reflection is lost on the low-angle side, while the representative reflections from (200) onward remain within the selected range. Increasing Qmax decreases the approximate real-space resolution Δr ≈ π/Qmax.
Method and limitations
d = a / √(h2 + k2 + l2)Q = 2π / d2θ = 2 sin−1(λ / 2d)Δr ≈ π / Qmax
This page reports geometric reflection positions calculated for a cubic lattice. It does not account for structure factors, atomic scattering factors, reflection intensities, instrumental resolution, detector efficiency, or background. “Covered” therefore does not guarantee that a distinct experimental peak will be observed.
Actual PDF quality depends not only on Qmin and Qmax, but also on corrections and normalization, background treatment, counting time, statistical precision, and high-Q signal-to-noise. The precise expression used for the PDF normalization can vary; Δr is shown here as a guide for Q-range design.