Magnetic structure fit: Co₂SiO₄ at 2.3 K, D20¶

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-cwl_cosio-d20_2k-cosio

Load the experiment¶

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

• pd-neut-cwl_cosio-d20_2k-d20

Add the relations¶

The project ties some parameters together from the start. On Analysis → Extra, add the aliases and constraints.

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¶

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 sixteen 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¶

Filter the Peak broadening 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.

Peak asymmetry¶

The low-angle peaks lean towards low angle. One FCJ term is freed; the other follows it by the project's constraint.

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

Atom positions¶

Co1 sits on a centre of symmetry and the other sites on the mirror plane, so only their free coordinates are fitted. The displacements stay at their room-temperature values.

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.

Magnetic moments¶

With the nuclear peaks fitted, the moments fit the magnetic peaks. The magnetic space group lets Co1 point in any direction and Co2 only along b.

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

Magnetic form factor¶

Last, the j2 term of the Co²⁺ form factor, which changes how the magnetic intensities fall with angle. It moves together with the moments, so it comes after them.

Filter the Magnetic form factors 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.