La₀.₅Ba₀.₅CoO₃ on HRPT¶

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.

Build the structure¶

On Structure, choose Create structure and name it, then set its space group and cell, add the atom sites and give each its displacement.

Create the experiment¶

On Experiment, choose Create experiment and its type, load the measured data with Load ▾ Measured data From web… from EasyDiffraction's collection, then set the instrument, the peak widths, the background points and the excluded regions, and link the structure.

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, 2θ zero and cell¶

The scale sets the overall height of the pattern, and the zero shift and the cell length put the peaks where they are measured, so they come first.

A group is freed in one action: choose it in the category filter above the table, then click the Free column header and choose Free · all.

Filter the Linked structures and Cell parameters, one category at a time, 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.

Background¶

With the peaks in place, the five background points follow the level between them.

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¶

The profile terms now fit the widths and shapes of the peaks.

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

Displacements¶

Every atom sits on a special position of P m -3 m, so there are no coordinates to fit. The displacements change the peak intensities with angle and come last.

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.

Constrain La and Ba¶

The correlations show the displacements of La and Ba moving together almost exactly, with opposite signs: they share one site and scatter neutrons similarly, so the pattern cannot tell them apart, and their s.u. are large. Give each an alias and constrain Ba's to follow La's, then fit again. Ba's displacement is no longer fitted on its own.

Filter the Atomic displacement parameters with [Ba] in their name using the category filter and the name filter, click the Free column header and choose Fixed · 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.