Rietveld fit: Si, SEPD¶

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-neut-tof_si-sepd-si

Load the experiment¶

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

• pd-neut-tof_si-sepd-sepd

Measured data from your own disk¶

Measured data can also come from a file on your own disk: on Experiment, Load ▾ Measured data From file… reads it into the selected experiment, or into a new one when none is selected.

Estimate the background¶

On Experiment → Extra, set the number of points under Background estimation, then press Estimate in the Background group on Main.

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.

Cell, scale and time-of-flight calibration¶

Filter the Cell and Linked structures parameters, one category at a time, using the category filter and the Instrument parameters with offset 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.

Background¶

The estimated points are a starting point; fit them now that the peaks are in place.

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

Gaussian widths¶

The background stays free while the widths join. diffraction-lib fixes it for this step and leaves it fixed; here the fit reaches the same result with it free, as every other case does. The Gaussian terms come first.

Filter the Peak broadening parameters with sigma_0 in their name using the category filter and the name filter and the Peak broadening parameters with sigma_1 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.

Lorentzian width¶

Then the Lorentzian term.

Filter the Peak broadening parameters with gamma_1 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.

Displacement¶

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.

Peak decay¶

The back-to-back exponential decay terms β₀ and β₁.

Filter the Peak asymmetry parameters with beta 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.

Correlations¶

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

Report¶

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