Rietveld fit: PbSO₄, laboratory X-ray¶

The same staged fit as the Python and Command line tutorials, in the app. Its structure and experiment come from EasyDiffraction's collection with Load ▾ From web…, and each stage frees its parameters in the Parameters table on Analysis before the fit.

Create a project¶

Press Start on Home, then Create a new project, and give it a name.

Load the structure¶

On Structure, choose Load ▾ From web…, search for each entry by its id and click it:

• pd-xray-cwl_pbso4-lab-pbso4

Load the experiment¶

On Experiment, choose Load ▾ Full experiment From web…, search for each entry by its id and click it:

• pd-xray-cwl_pbso4-lab-lab

Set the minimizer¶

On Analysis → Extra, set the Minimizer as the case's project does: the Shift/s.u. stop rule and room for more iterations.

Start with nothing free¶

On Analysis, open the Free column header of the Parameters table and fix every parameter, so the stages below free one group at a time.

Scale and 2θ zero¶

The 2θ zero first: freed together with the cell from the start, the two pull against each other and the fit cannot take a step.

Filter the Linked structures parameters using the category filter and the Instrument parameters with calib in their name using the category filter and the name filter, click the Free column header and choose Free · all, then press Fit in the status bar.

Cell¶

Filter the Cell parameters using the category filter, click the Free column header and choose Free · all, then press Fit in the status bar.

Background¶

The six Chebyshev terms.

Filter the Background parameters using the category filter, click the Free column header and choose Free · all, then press Fit in the status bar.

Peak widths¶

Filter the Peak broadening parameters using the category filter and the Peak mixing parameters with eta_0 in their name using the category filter and the name filter, click the Free column header and choose Free · all, then press Fit in the status bar.

Peak asymmetry¶

Filter the Peak asymmetry parameters using the category filter, click the Free column header and choose Free · all; then type a1 in the name filter and choose Fixed · all in the same menu; then type b1 in the name filter and choose Fixed · all in the same menu, then press Fit in the status bar.

Lead and sulphur positions¶

X-rays see the heavy atoms first, so their coordinates come before the oxygens'.

Filter the Atomic coordinates parameters using the category filter, click the Free column header and choose Free · all, then press Fit in the status bar.

Oxygen positions¶

Filter the Atomic coordinates parameters using the category filter, click the Free column header and choose Free · all, then press Fit in the status bar.

Displacements¶

The correlations after this stage show how far the oxygen displacements can be told apart; the case keeps them separate.

Filter the Atomic displacement parameters using the category filter, click the Free column header and choose Free · all, then press Fit in the status bar.

Correlations¶

The Correlations view on Analysis shows which fitted parameters move together.

Report¶

The Report page collects the structure, the experiment and the fit.