Step 6 - Set up Refinement

Time to refine. We’ll need two processing layers - one to calculate the g(r) and S(Q) from the simulation, and one to refine it against experimental data.

As noted in the introduction we have neutron-weighted experimental data, so we need a layer to calculate g(r) and neutron-weighted S(Q) for our three experimental datasets:

Layer ⇨ Create ⇨ Calculate… ⇨ RDF and Neutron S(Q)

Show the module palette for the layer by clicking the Show Palette button at the top left of the tab

Drag two additional NeutronSQ modules from the Correlation Functions in the Module Palette on the left, placing them after the existing SQ module

We need to set the instrumental broadening in the SQ module first:

Click on the SQ module to display its options

Set the QBroadening to OmegaDependentGaussian with a FWHM of 0.02

Now let’s set up the three NeutronSQ modules to calculate what we want:

C₆H₆

Click on the first NeutronSQ module to display its options

Change its name to C6H6

Open the Reference Data settings group

For the Reference keyword select the file C6H6.mint01 and set the format of the data to mint instead of xy

C₆D₆Edit

Click on the second NeutronSQ module to display its options

Change its name to C6D6

In the Control section click the Edit… button for the Isotopologue option

Press the Add button to add the natural isotopologue for each species present

Change the isotopologue from Natural to C6D6

Open the Reference Data settings group

For the Reference keyword select the file C6D6.mint01 and set the format of the data to mint

50:50 Mix

Click on the third NeutronSQ module to display its options

Change its name to 5050

In the Control section click the Edit… button for the Isotopologue option

Press the Add button to add the natural isotopologue for each species present

Select the entry for the benzene species, or its isotopologue, and click the Add button to insert the next unused isotopologue (i.e. the deuterated analogue)

Open the Reference Data settings group

For the Reference keyword select the file 5050.mint01 and set the format of the data to mint

All that remains is to add our EPSR refinement layer:

Layer ⇨ Create… ⇨ Refinement… ⇨ Standard EPSR

Select the EPSR module to display its options

Change the EReq value to 10.0 - the default of 3.0 will not be enough to promote the necessary changes in structure

---

Previous Step Next Step