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PWDR Reflection Lists subdata tree item (Powder Diffraction)

This window shows the reflections for the chosen phase (selected by the tab at top) found in this powder data set. It is generated by a Rietveld (including Pawley and LeBail) refinement. Reflection d-spaces are generated directly from lattice parameters but \(2\theta\) (or TOF) values will incorporate corrections, such as for sample displacement, zero, etc. The values of various correction factors, I100, size and mustrain terms for each are also shown.

The powder diffraction reflection list shows the reflection widths, accounting for instrumental as well as sample effects (the latter can be anisotropic), where the columns labeled as "sig2" and "gam" show the Gaussian and Lorentzian components for the width. The "sig2" value is the variance of the Gaussian contribution to the peak (\(\sigma^2\)), while "gam" is the full-width at half maximum (FWHM) for the Lorentzian component, \(\Gamma\). Note that the Gaussian full-width at half-maximum is given by \(\(FWHM = \sqrt{8 \sigma^ 2 \ln 2 }\)\) while \(\Gamma\) is the Lorentzian FWHM. The \(\sigma^2\) values (peak variances) are in units of centidegrees\(^2\) (centidegrees are degrees*100) for CW data or microseconds\(^2\) for TOF data; \(\Gamma\) has units of centidegrees or microseconds.

What can I do here?

  • The indices (hkl values) for reflections can be displayed by letting the mouse rest at the position of a reflection in \(2\theta\), Q, etc. in the PWDR plot (the vertical position does not matter) for reflections in the phase selected as a tab in the data window. A "tool tip" with the reflection indices will be displayed for any reflections close to the lateral mouse position.

  • Right-clicking on a reflection tickmark will cause an hkl label with the indices for nearby reflection(s) to be displayed. Once a reflection label is shown, it can be dragged to a new position vertically with the left mouse button. Right-clicking on the label will delete it. All hkl labels can be deleted with a menu command. The hkl labels, including their positions, are saved in the GSAS-II project (.gpx) file.

"Reflection List" Menu Commands

Note that some of these commands are more useful for HKLF (single crystal) histograms.
  • Select phase – if there is more than one phase; you can select another phase; the window title will show which phase is shown. You can also simply select the tab for the desired phase.
  • Plot 1D HKLs – shows a stick diagram scaled to Fc2 for the reflection for the selected phase
  • Plot HKLs – shows a HKL layer with rings scaled to F or F2 for Fo and Fc. +/- steps through the layers and h,k or l selects the orientation – see K box for all the possible commands.
  • Plot 3D HKLs – shows a 3D representation of the unique part reciprocal space points for this phase. The save as/key item in the plot status bar shows the various commands for modifying this plot.
  • Wilson statistics – displays a Wilson plot for the intensities.
  • Show/hide extinct reflections – can exclude space group extinctions from the list (not valid for PWDR data).